Hi I've recently bought an AW11 which I plan as having as a street driven track car, nothing serious just a hobby.
The car makes plenty of power but the suspension is stock/10yrs old. I am thinking of buying the complete suspension overhaul package with the koni insert upgrade from twosrus.com:
http://twosrus.com/catalog/product_info.php?products_id=219
 
From what I have read on this site there's no middle ground, I'm on a somewhat limited budget but at the same time I don't want to have to upgrade in the next 6/12 months because I was too tight the first time.
If anyone has any advice or experience I would greatly appreciate it.

I don't think anyone who has put Koni (yellows) on their AW11 has regretted it.  Excellent range of adjustment from nice and soft to very stiff.  That isn't to say the KYB's of that package are bad I can't comment, but personally I think Koni's are great.
 
Would much rather have Konis than D4/G2 coilovers (which I have atm and dislike). 
 
Unless your current dampers are shot have a think about just replacing all the bushes and ball joints now and then save for the Koni inserts.

I have Koni Adjustables with the stock springs & find that quite a good mix. As Rob says, you can dial them hard for track days & then back to soft to cope with our wonderful roads!

Just digging up this thread to add a couple of cents.
 
The twos suspension package has some great stuff in there, things which are pretty much "must haves" for any adub. The tie rods are brilliant, not only do they make adjustment a doddle, but they also use the "front style" outers which are ridiculously cheap to source for the future. The prothane kit makes a world of difference too, and the other bits and bobs are definitely worthwhile on a car this old.
 
But the koni's are so, so much better than kyb's. I recently flipped a set of BC coilovers for some stock struts because the car was just way, way too stiff for my needs (although it did have awesome stance). The "new" struts were fitted with kyb "climb gear" inserts, and they have the same horrible linear damping that you find in most coilovers and end up being harsh yet underdamped.
 
I've had koni's in two other cars over the years, and they just make a world of difference. You get compliance without wallow because they use velocity sensitive damping (eg. digressive), so the wheels can get out of the way of sharp bumps, but resist compression from pitch and roll like much firmer dampers.
 
I loved the hell out of them with stock springs, it made my car ride "european" (but not bad euro, eg modern german), but i found them to work even better with slightly firmer linear springs.

I'm running Koni yellows and TRD springs, and have no issues with stiffness, they ride beautifully. I can't really compare to anything other than the tired stock suspension I had before I installed the Koni's, but they're easily adjustable (on almost full hard they're a bit jiggly for the road, but nice and firm on the soft setting without being too brutal over bumps). The suspension crashes a bit over big bumps, but as I said - they've held up so far (only done about 3000km though :)). Also got Koni yellows on the mini after having brutal coil-overs on it when I got it - very happy with those ones too :) . They're a bit pricey up front, but you won't be worrying about leaky shocks 10,000km down the road - have heard some pretty average reviews about some of the cheaper stuff out there.