Turbo swap

I presume you currently have an NA?
 
If so then just assess the good/points of the rest of your current car.  If you have had it for a while then you know what is good what is bad etc, and know what you have, and evaluate if its worthwhile doing a swap.  Its fairly easy to do esp if you have a half cut.
 
Getting a complete car is obviously easier but you have the aspect of not knowing what you are buying.
 
Just weigh up the pros and cons of each option, including if you will be doing a swap or paying someone to do it, availability of half cut compared to turbo car etc, and make an informed decision.
 
Cheers

From what I understand is you want a half cut so you can swap everything over including the harness. Even still there is a chance of having to rewire/repin some plugs.

You will also want to add in the costs of doing the timing belt water pump hose from help ect.

There has been a few people on here that have done it so if you do a search it will help.
Evil138, bionical are 2 people that I can that I can remember

On the flip side, for the price of a good half cut, you could buy a turbo, source a manifold to suit (stock or otherwise), source some bigger injectors, buy an aftermarket ECU and turbo your NA motor. The high compression NA motor with a turbo will be pretty responsive and with a good tune should be as reliable as a stock motor, power figures should match or exceed stock turbo figures. If your not abusive to your NA gearbox, it will handle the turbo (hell there are supercharged V6's in the UK running the S54 box...) and you will have a lighter setup running the NA gearbox, drive shafts and hubs in comparison.
 
The downside is, if your planning to go for big power in the near future, the high comp build will probably run out of head room rather quickly due to the compression and cams.

3sgeTurbo
You can tubo the n/a motor - I have been there and done that,

What was your opinion of the NA+T build compared to a factory turbo?

Ditched the Beams hey?
I know most ppl here are saying do halfcut or turbo the NA but just me, personally, I would just sell the NA car and get a good condition Rev 3+/Gen 3 and be done with it. I just don't want to go thru the hassle but maybe you enjoy working on it. Unless ur really attached to the NA (just give some time to let it go lol) then selling and buying would be "easier" for the non-mechanic type like me...
The NA should go to a decent home :)

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

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.