Just to let Austinites that don't already know about it, there's a newer game store that sells older classic game stuff (as well as some newer, XBOX/PS2/GC). It's called GameOver and is located in that little strip center at the corner of Lamar and Anderson (near where 183 crosses over Lamar, South of the Bingo Hall across Anderson).
It's a pretty small place, but has some neat classic games/systems as well as some gamer related T-Shirts. The store buys older stuff too. It's basically a Mom & Pop (well, just Pop as he owns/runs the store) type smaller shop. So, if you are looking for something of the classic stuff that GameStop/EBGames doesn't carry, ya may find it there.
PS: No, I'm not associated with the store in any way. A local game store clerk told me about the store (he shops there too) and I just thought I would pass along the info for those that didn't already know about it.