I agree with what Mazer said about the AV123 x-series speakers. If you go with the x-mtm towers at $339/pr, the x-cs center at $129, and x-ls bookshelves at $165/pr, it leaves you $367 for shipping and a sub. I would recommend you save up a little more for a decent subwoofer by SVS or HSU.
If you don't like the x-mtm towers, then get another pair of the x-ls bookshelves for $165. This setup with 4 bookshelves and the center channel comes to $459. You could get a HSU VTF-2 MK3 sub for $499. Or, once again for a little more, get a better sub by HSU the VTF-3 MK3 for $629.
If you can't save more and need a discount subwoofer, look at either: HSU STF-1 ($254), HSU STF-2 ($349), Dayton SUB-120 ($139), or Bic Acoustech H-100 ($249)