video cards

[me-5yx05kfkO/aqeI1yJSURBw at public.gmane.org (Matthew Gillen)]

My nvidia card from 2 years ago is flaking out on me (flickering the display
for a while, then locking up my computer).  Once I removed the nvidia card
and relied on the onboard video, everything was stable, so it must be the
video card going bad.

So I'm wondering what the current state of video cards are for linux.  Is
ATI finally back in the game or not?  I'm looking for something that is
mid-range (it's replacing a Geforce 8600) to play games in windows (nwn2),
and also be a mythtv frontend (in linux, with full HD playback).

And, since I've already been burned by this when they did their last
naming-scheme change, what do the various numbers/card-names mean for ATI
and Nvidia?  Nvidia seems to be going back to 3-digit numbers, which bugs
me.  I figured out their 4-digit system the hard way: the most significant
digit was the generation marker, and the *third* digit indicated how
high-end the card was (an 6800 was higher performance than a 7300).  So how
do the 3-digit ones compare to, say, a 9800GT?

Thanks for any insight,
Matt