Hey CompFreek, Those dudes rippin' on your system can blow themselves. (Notice the period)
I guess some people just don't have anything better to do. A K6-3 is a realy good proccessor, just not the top of the line. My "Other" PC is a K6-2 350 OC to 400 with a 16MB TNT2 and the only things I have had trouble running at very playable framerates is F1-2000 and Mech4. All it takes is a bit of tweaking the graphics settings and they both run fine though. I would imagine that an OC'd K6-3 with a G-Force Anything would be nice. I am running a Duron 700@900@113F with a Maxi Gamer Cougar PCI! (TNT2 M64) and everything I have runs great. Take 300Mhz and a bit of tech from the processor, Add a BAD ASS GPU and I think it'll be all good.
P.S.
Do you have enough memory??
Also, if you have any freaky problems with reboots or crashes, check around to see that your Mobo is giving the card enough power. I hear that those cards draw a lot of juice.