They offered 3 different engines. 2 1.8T's and a 3.2 V6. The first 1.8T had 180hp, k03 turbo (the MKIV GTI engine) and is available in AWD or FWD. The second 1.8T is the one to get, its called the 225. It has 225hp out of a K04 turbo and upgraded internals. They run low 14s stock with a manual and AWD only. For 2004 they offered essentially an Audi R32. 3.2 V6 with DSG transmission. Also runs low 14s.
I would get the manual AWD 225. With a chip, they are beasts and have much more potential because of the K04 turbo. Same common problems with any Audi/VW. Timing belts, coil packs, window regulators etc.
Hope this helps. I don't think you can go wrong with any TT besides the FWD version.