That's pretty difficult. Here's an option:
3x
NXG Pro 4.1 satellites -- $131.46 shipped -- Use these for your front stage (left, center and right)
NXG NX-BAS-500 subwoofer -- $269.99 shipped
Total for now = $401.45, not including
speaker wire or a
subwoofer cable.
Then later, when you get a little more mad money, add a pair of
Fluance XLBP for your rear surrounds.
While you're shopping for speakers, there's something you ought to bear in mind. If you're going to be wall mounting your speakers, you probably ought to avoid any rear-ported speakers. Those NXG satellites have an aperiodic port on the top, and the Fluance bipoles are front-ported. Plus, they're a bargain and they sound nice for the money.
Well, I haven't heard the NXG's personally; but those who have, recommend them highly.