8v GTi's get a bit of stick, but I think once you've taken some weight off you'll fall in love.
Suspension is a must, a stripped car on standard suspension is a deathwish.
If you were thinking about more power, as Mr.Smiles said, the 16v engines are punchy.
You can pick one up for peanuts nowadays and the swap wouldn't be hard compared to a 20vT.
The route I've taken is to buy and engine and work on it while its outside the car, It's easier,cleaner and you'll learn lots.
Then... when its a force to be reckoned with, or when you are getting bored of 8v. Bang it in!
Best of luck. I'm sure this forum will help you loads.