Why would it overheat? I have a Sapphire Ati Radeon 9700 and it never gets that relly hot. I don't think u should wory about that. I've never heard of people having heat problems with a Radeon.
Re: radeons
All the 9000 cards have dx9 support.
U guys should check out some reviews.
Here u go:
http://www.anandtech.com/video/showdoc.html?i=1797&p=6
http://www6.tomshardware.com/graphic/20030311/geforcefx-5600-5200-03.html#unreal_tournament_2003
Imo 30 fps is crappy, but it does depend on the game how much u feel the slowdown, in HL u can relly feel when the fps is lower than 60, but in some games u don't. But imo 30fps is way to low to relly enjoy a game. Should be atleast 40fps all of the time.