If you're only worrying about MAME, I'm pretty sure it won't make a difference at all. MAME doesn't rely on the video card nearly as much as the CPU. Andy probably just started using the 9200 chipset because the 7200 was discontinued (?) or the 9200 just became more cost efficient.
You're not going to see any major improvements in your gameplay if that is your question. I wouldn't worry about it too much. If you do wind up getting a new one though, sell me your old one cheap
