If it were me I'd start with a pair of Ascend Acoustics' excellent
CMT-340SE speakers for $608 shipped.
Outlaw Audio has their
LFM-1 Plus subwoofer on sale for $500 with free shipping.
Add a factory refurbished
Onkyo TX-NR709 receiver for $450 plus shipping and you're only $50 over budget and will have a kick butt 2.1 system. Add a CMT-340SE center and CBM-170SE (or HTM-200) as surrounds when money allows.
If you must have 5.1 you could substitute five Ascend Acoustics CBM-170SE bookshelves ($750 shipped), use the same subwoofer ($500 shipped), and a refurbished
Denon AVR-1713 for $330 and be about $100 over budget. I would start with the 2.1 option and build on that as money allows but this would still be a really nice system.