For a $1k budget you're better off with a single card, like a 4870 or a 4890.
SLI/Crossfire is more noisy, more expensive, and eats more power. Also, 2 cards doesn't mean twice the performance, there is about a 50% increase from 1 card to 2.
I would go with AM3 790FX or 790GX type of motherboard with ATI video card. The memory same brand you what is the DDR3 1333 is $10 cheaper. It better to upgrade with a different CPU and faster memory in later.