Oops, I've been ignoring this forum. Neglecting it. And now people need my attention! To the basement!
@Jjay: I'm not a pro at modding cases, sorry. I've fabricated my own radboxes and dremeled some metal out of my current rig, but I have no idea what your e520 looks like internally. Not sure if cutting into it is a good idea, structurally, but I could take a look. A better option, however, is probably upgrading to a more roomy case. Good cases are important, second only to good power supplies in importance. Forget a good CPU or graphics card, if your case and PSU suck then you're already looking at a bumpy road in the future. Just some friendly advice.
@Traize: $500 is a little slim, but you CAN make something that WILL play Aion decently with it. Not awesomely, but it'll play.