Dan, I mentioned the above to you the other night. If you've got your car the way you want it, and you've clearly put a lot of effort into her. If you can get the TT6 conversion done reasonably, then go for it. The only thing you have to weigh up, is the price of carrying out the work, in comparison to selling and buying a complete car.
The engine and turbo isn't your real issue I'd say, it's the 6 speed gearbox and gubbins that go with it, as you probably already know, the 6sp gearbox is not cheap
Edit - in fact, think of it this way, I reckon you're looking at 5k to do a 6spTT conversion. If you sold your car for 4k, then added 5. you could get a very nice 6sptt for that money