I have a 91 Turbo here with koni yellow inserts and lowering springs (not sure which brand), 18" rims and front sway bar reinforcement plates. I'd like to upgrade my suspension and I'd like some advice for the best bang for buck. It's a week-end car.
 
I was thinking about upgrading my front sway bar (whiteline) only. Does that seems like a good idea? Prothane bushing kit from Two'r'us is supposed to be good but it looks like it's a lot of work to install and I am not sure if it's good value for money. I heard mixed reviews about the usefulness of an aftermarket rear sway bar.
Should I get the adjustable endlinks as well and do they do much? Or do the prothane bushing first, then look for upgrading the rest later?

Best bang for buck in my opinion would be a set of BC coilovers, only upgrading the front swaybar can cause some issues with under steer. Bush kit is a good start I would also recommend checking all ball joints and upgrading to the urethane engine mounts. I have also installed the Megan racing adjustable front tension rods and adjustable rear trailing arms. My sw20 feels really good to drive very responsive feels good on the track and still well behaved on the road.

+1 with BC coilovers.

I have had two sets and think there the best for value, seem to be a better ride on the road than a friends TEINs
and half the cost.

I have my BC BR coilovers, a whiteline front sway bar, new ball joints, tie rods and rack ends and she handles great. very responsive, the way my coilovers are set up with the front bar, i have ZERO understeer in the dry, and very very little oversteer its all very stable.
Stock rear bar.

Also, the BC BR coilovers come with stronger front endlinks.

Thanks for the suggestions.
I never thought about upgrading the engine mounts. I honestly had no idea what that would do until I have done a bit of research on that a few minutes ago. It seems like peoples either love or hate them though. I am thinking about getting them. I do have quite a few things rattling in the cabin already though, so I should probably try to fix these first or it's going to drive me crazy with stiffer mounts...
 
Not super convinced about the coilovers tbh, I had some (sleeve type) on my previous car and I didn't care all that much for them. Wouldn't lowering springs work the same way anyway (other than not allowing you to go as low and having as much control, but honestly, after finding a good height, I am not sure why I'd ever want to mess about with the height again)?
 
Cheers, I will also have a look at the ball joints and tie rod ends to see if they need to be replaced. And I guess I probably shouldn't just upgrade my front sway bar after all with my current setup?

With base height adjustable coils you can lower the car without impacting handling as much as lowered springs, as you arent reducing the shock travel. So there is a good advantage. a decent coilover is a great upgrade :)

It all comes down to your budget. The BC is a great base line coilover but for $1500-$2000, I would highly recommend the Spax coilover. The support with set up and ongoing development is very good.
I think the coilover allows for easy fitment of different spring rates for tuning the car. Also allows you to tune the rake of the car to help with set up.
Go with the bush upgrade but do not replace a OEM spherical bearing with a Nolethane bush or the likes. Big step backwards.
I would not bother with the swaybars. Just get the spring rate correct and you should be ok with standard bars.
The adjustable end links are for resetting the swaybar after lowering the car. If you don't go too low you will be ok.
Spending money on eliminating bump steer and improving roll centres is a far better way to spend money instead of sway bars. Infact, I would start here if I had my time again.
If you are going to the track, get some 17's or 16's. 18's are just too big and heavy effecting braking, accelerating and cornering.  
 

It all comes down to your budget. The BC is a great base line coilover but for $1500-$2000, I would highly recommend the Spax coilover. The support with set up and ongoing development is very good.
I think the coilover allows for easy fitment of different spring rates for tuning the car. Also allows you to tune the rake of the car to help with set up.
Go with the bush upgrade but do not replace a OEM spherical bearing with a Nolethane bush or the likes. Big step backwards.
I would not bother with the swaybars. Just get the spring rate correct and you should be ok with standard bars.
The adjustable end links are for resetting the swaybar after lowering the car. If you don't go too low you will be ok.
Spending money on eliminating bump steer and improving roll centres is a far better way to spend money instead of sway bars. Infact, I would start here if I had my time again.
If you are going to the track, get some 17's or 16's. 18's are just too big and heavy effecting braking, accelerating and cornering.  
 

Thanks for the feedback :)
Still not super sold on the coilovers, even though everyone seem to be loving them. If they weren't that expensive, I would probably give them another go.
I bought the kirkausaurus engine mount that someone recommended (mostly because they were cheap and are easy to revert back to stock), and I will probably get the bushings if I can get someone to install them for a good price. I also mostly gave up on upgrading the sway bars, at least for now.
And yeah, I want to get smaller rims, probably 17" rims. I just need to find a good deal on a 17" rims and tyres package.

A cheap Coilover is unlikely to give you many (any) advantages over a well sorted conventional set up. You can get a wide variety of spring rates and ride heights for a standard strut and will work fine provided you are not looking to get super low. Have a go at doing the Prothane bushes yourself - it's not too hard. Replace the ball joints, make sure the steering rack is in good shape and get a good alignment. Some nice light 16s or 17s and you will be set.
I actually asked Just Jap about putting lower spring rates on a BC Coilover and they said it would void the warranty. Made me think they hadn't got their length and bump stops right. It stopped me buying them and I went for the Konis. To get a real improvement you would need to spend some serious bucks on some custom bilsteins or MCA racing but that is pretty serious gear for weekend/track day car.

So, I went to a suspension shop today since my car was getting really bouncy and apparently I need 3 new lower ball joints, new rear sway bar bushings and new shocks all around ;/
I am looking at my options. Right now I am thinking either BR BC coilovers ($1300) + 3 ball joints from amayama ($120 + shipping)
OR
4 koni inserts + 4 ball joints from Two'R'us ($700 USD + $250 USD shipping).
 
Coilovers sound more exciting BUT I doesn't look like they would fit with the rims I just bought a few weeks ago ;/
17"x7" +45 (no tyres on them yet); so it looks like I don't really have much of a choice unless I buy new rims, do I?
Thoughts?