Probably not going to happen on that budget. The used route is likely your best bet, although I'd suggest you start with a decent quality stereo receiver and two nearfield monitors like the Behringer 2030p and add a sub later when you've saved up some more. Most of the "computer speaker" packages from Klipsch, Altec, JBL, etc. just can't even come close to keeping up with a setup like that, trust me I've owned or listened extensively to several of them.
