The case/PSU that mpilchfamily is referring to is probably the Antec Sonata II with a 450W PSU. You can find it for $106 at pagecomputers.com. This is over 20 bucks cheaper than Newegg.
EDIT: Newegg has an instant savings of 10 bucks putting this case 13 bucks more than pagecomputers.com.
Personally, I don't think SLI or Xfire is worth it. You can save almost 60 bucks right of the bat by getting the ASUS P5B-E, Abit AB9Pro, or the Gigabyte GA-965P-DS3.
But if you want SLI capability then this
ASUS P5NSLI - $120 is the only board that I know of that will currently allow you to use SLI with a C2D. Though this might have changed. Don't know. It's 80 bucks cheaper than the ASUS P5B Deluxe which would allow you to get 2x1GB sticks of memory.
You never mentioned overclocking. That memory will only be beneficial if you overclock. If you don't plan on overclocking then this
PQI Turbo 2x1GB for $180 is a bargain.
For the video card, I'd get the
X850XT PE for $126. It's faster than the stock 7600GT. Against the OC'd XTX 7600GT, I would assume it'd still be faster since the X850XT PE pretty much destroys the stock 7600GT.
These
benchmarks only allow you to choose the X850XT vs the 7600GT. The X850XT PE is only going to be better.
Now, if you have to have a card with SM3, then the 7600GT is the "mainstream" card to get.
I'd recommend getting the
Seagate Barracuda 7200.12 250GB Perpendicular Drive - $80. It's only 10 bucks more but it's better than the one you selected threefold. First, it has 50GB more space (more bang for your buck). Second, it has 16MB of cache instead of 8MB. And third, it's a perpendicular drive.
The E6400 is a good choice.
Total: $912 (with P5NSLI mobo) or $35 more than the system you put together.
EDIT: If you have a case that you can reuse, then get this
Enermax Noisetaker II - $89. This is only 17 bucks less than the combo but this PSU is much better than the one that comes with the Antec case.