Yeah, unfortunately collecting for GBA is too damn expensive. You're lucky if you get good deals!
DS is more affordable, and have got 50+ titles in my collection. Need more of them!
I have quite a few DS games sealed as well as a ton of PS2 games sealed, only a few PSX and GBA sealed though
THE BEST METHOD to run PSX games (and everything else for that matter) is via Retroarch - http://buildbot.libretro.com/nightly/
If you have any questions on how to set it up on Windows please feel free to ask, its very easy.