My N/A kicked ass hard, some times I miss it, it only had basic supporting mods like injectos, reg and ecu but power came on really srtong and pulled right until redline. I believe this was because of the N/A inlet manifold having very long runners to give it heaps down low and the bigger N/A cams help out witht he spool and top end.
 
Also I come from a family of mechanics so I did all the work my self, if you were to take the 3sge+Turbo route and have to pay someone to do all the mechanical / electrical work then it would cost $3000 easily.

Also you could always blot and SC14 supercharger on with an AFC, would be cheap and kick ass hard!

Can you quickly clarify (pics help too) exactly what you've done to your car. Much easier to give a suggestion on which is the better the option. At a guess, you'll be better off buying an original MR2 turbo with some nice select modification.

Turbo swap is not that hard. 
 
I did it with a Gen 3 halfcut (around $3000 from memory) and it had everything needed for the swap (obviously replace the timing belt, water pump and fuel pump while its out).  The best thing about the swap is that its all OEM so there aren't too many 'bugs' to sort out when finished, as long as you swap everything from the halfcut over. 
 
Like others have mentioned, the only difficult bit is wiring up the loom, but if you sit down and label all wires on the NA side, and all on the turbo ecu side, your pretty much sorted.  It does take time, but its not rocket science.  Speedo is also a no go - either remove the electrical sensor in the Gen 3 with mechanical or swap in a electrical cluster dash (I'm currently in the process of swapping an electrical cluster in).
 
Additionally, I have all my notes and a few writeups that I used when I did mine so if you or anyone else needs help, PM me and I'll send them through. 

Hmm judging from all this and really thinking hard about it,
My engine is 220xxx kms old and needs new rings so a bolt on turbo is out,

The turbo swap could work but I can't afford the downtime. As this is my only car.

I think I will have to just buy a turbo after searching for a while, and finding the right one
Only after something moderate and half reliable 200-230atw I would be happy with.

Then after acquiring a turbo and am happy with how it is then sell my Na, be a shame to see her go :(

I just would like to make some money back on buying a turbo.
Ill see what happens over the next few months.

Thanks everyone for replying big helps
Thanks mr2qik aswell :)

Well dosnt need new rings exactly, just would if I ran 10 pounds of boost through it would be up for a rebuild.
Heads been rebuilt tho and 184 across all four cylinder which isn't far from stock. Little bit of build up but hey she's 23 years old

Where do you buy your halfcut

I got my halfcut through a mate who ownes a tuning shop up here called High Tech Tuning.  He goes over to Japan all the time and sources engines, import parts and cars which I felt comfortable about. 
He also tested the engine in my halfcut before passing it on and I havent had a major problem with it since (touch wood) and that was nearly three years ago. 
Not sure where you are but maybe try Gorilla Industries or PM some of the others guys who have done swaps.  Artymr2, Darius, Bionikal...

Can you post a pic of your car & its current condition? Not certain, but I bet the numbers would favour selling & buying another example, capitalising on money spent by another seller. You can get a nice example for $10-15k, which isn't much compared to working with what you've got.

Buy a turbo one then sell yours.  This way you can wait until the perfect one becomes available and also swap over any OEM parts from your current car that are in better condition plus aftermarket parts etc.
Too much hassle doing engine conversions I reckon these days as the factory turbo or already converted cars are cheap and mechanic hourly rates are high to have the conversion done to your own car.
My 2c