If you're going to buy a GeForce2 Pro, you probably want to get a new CPU first, as the Pentium II will be a severe bottleneck to the new graphics card.
If your GF2Pro's performance is going to be reduced by a slow system, it isn't worth the high price. Get the CPU first, then the graphics card.
fcchin has a pretty good point about the price of the GeForce compared to that of a whole Duron/Thunderbird system. Definitely worth a thought or two...
you will benefit the TNT2 better with a cpu upgrade than you would benefit the 448 with a GTS graphics card..