No need for 680i SLI with a 20" monitor. SLI as an upgrade path is also a bad idea, because there will always be a better single card solution, unless you plan on getting a 24" LCD or larger. You could always sell your old card to offset the cost of a new card anyhow. So, drop down to a less expensive board, like the MSI P6N SLI-FI, the eVGA 650i Ultra, or the GA-965P-DS3 (from clubit.com). If, for some strange reason, you only want Asus, get the P5N-E SLI or the P5B-Plus.
I agree with Trevante, go with the 400GB drives instead. They're a bit faster than the WD2500KS drives (which are pretty damn slow).
Also, the 620W Corsair is cheaper ($145 - $20MIR = $125!) from buy.com with the
10% off coupon.