A 2.0GHz Intel CPU with a decent graphics card, should game adequately - with a TNT2, only games of about 5 years ago or more would be usable.
In AGP, the 9800 (nothing, PRO or XT) should be a decent card, without spending an insane amount (unless you are commited to keeping the AGP card in your next upgrade, by which time AGP could be on the wane) - at the moment, you can get motherboards with either, though it seems, not BOTH (there may be a few).
Another "hedge your bets" option, is the the few AMD motherboards that can take the cheaper 754 OR the 939 - only to be recommended if you have thoughs of going for a cheaper 754 CPU now, with the option to upgrade, as the ones reviewed normally have a weaker chipset than a "performance" 939.
But unless there is something else wrong, all you really need is a decent AGP card in your current system - that kind of machine should never be carrying a TNT2 - even a Geforce 2MX is more powerful - and that is now the kind of thing you find on computer fair junk tables - most importantly, the TNT2 does not have any hardware T&L capability, and that is a basic requirement for any games of the past few years - and that is now left behind by the directX 8 and 9 capabilities - and you can get a once-great card like a Radeon 8500 or Geforce 4 Ti4200 (both good DX8 hardware) pretty cheap - a bit dated now, bot still a couple of orders of magnitude better than a prehistoric TNT2