Just put a new rig together just for flying AH (tried to convince my wife it's for my telecommuting with little success ;-)
Anyway, I found that
1. I have 19", didn't matter @ 1024 res, 16 bit
2. I run now @ 1280, 32 bit and it's a _big_ difference. I can spot Ostis all of a sudden, I can read bogey maneuvers @ 1K which I couldn't do before. With a seat far back I can read instruments much better. Short: more kill, more fun.
3. I took a Abit K7RAID board, a thunderbird 950Mhz (easily overclocked to 1Gig, runs around 65C, more later) and I'm happy like a pig in .... with my TNT2. My framerate @ 1280 stays almost always above 20, only smoke kills it to 10 or 12. Basically seriuosly smoother than my old PIII 450. That makes a BIG difference, especially for gunning @ 0.7, 0.8D. That hjappens quite often if I don't catch a guy in a zoom down to 0.4D or the guy tries run away & you get a steady shot. Of course I couldn't help it and ordered a cheap GTS ;-)
There is a very good review in CombatSim how to put such a rig together & overclock it. My experience: buy a rather fast processor and don't try to get the voltage up too much. It gets real hot real fast. I spent 1/2 day figuring out that I put a cheap heatsink wrong direction and didn't have contact. Box would half-boot & freeze. Got an orb into it now and it's better but I had to put an additional fan right @ the CPU in. Advice: get silver paste or heat-silicon, a _good_ heatsink [copper] and make sure it fits well.
So overall, yes, if you can blow the 300$ for CPU, 150$ for board, 100+$ for memory [get 133 if you can], go and do it but I'd say, get at least a TNT, better TNT2.
BTW, I hope pretty soon AH will display the 3dMark score with the icon ;-)