Which Nvidia card should I buy?

OS: Win98 and XP (on two separate drives)
CPU: AMD XP1800
MB: Shuttle
Monitor: Daewoo 19" 905D

I currently own a Nvidia FX 5200 by Megaspeed (MS). I bought it because it was
very cheap and I wanted to test the waters, as it were. If I upgrade from here,
which Nvidia should I buy? I might could afford around $300+ (I would have to
sell allot of stuff on ebay first, LOL).
I am used to the ATI Radeon 9700, but because it has no Stereo-3D support I'm
probably going to be selling it (I actually downgraded to the Nvidia FX 5200 so
I could test Stereo-3D).

So, is the GeForce FX series the one I want? That is, should I just shoot for
the highest FX model I can afford? Is the GeForce FX 5900 the best nvidia for
consumers? (All the other models on the nvidia site didn't look like they were
for game playing or regular consumers). Is the FX 5200 so inferior that I should
upgrade now? Or just wait for the next Nvidia offering?

Thanks for any info.........Sam