Ilikepiedoyou:
You could get what you have, or you could get a Core 2 Duo and
this motherboard will offset the cost. The only real difference is some of its expandability, and those differences are minor. I don't foresee a need for a PCI-Express x4 slot, unless you want to spend money on a RAID array or possibly a PURE card (since those cost as much as a new system, and they're not out for PCI-Express yet anyway). Either way, you may run into issues with upgrading to a quad core chip on a budget motherboard. Just because a chip fits in the socket doesn't mean that the mobo will meet its power requirements.
As for that free PSU, you might be getting what you're paying for. Don't be surprised if you have to plunk down the cash for a good one if this dies on you. Since it is free after rebate, you don't have much to lose. Just make sure it will support PCI-Express and SLI.
For your hard drive, get a good SATA hard drive from Seagate or Western Digital with a large cache (8-16 mb). You'd also be surprised how much space you'll need if you want to render out to frames all the time. 100+ gigs is decent, but for the cost, 200-300 gigs will give you lots of headroom.
Google for some reviews for good cases. After all, you're going to have your hands in there putting this thing together. You might as well get one that is decent to work in. You don't want cramped space, sharp edges, or the covers for your spare slots to be cheap punch-outs (they can damage your system when you are upgrading if you are unlucky). You also want good cooling since this is supposed to be a stable workstation. I wouldn't get one that is super expensive unless it was BTX-upgradable. But you were looking to save money anyway.