You can pick up an other 6870 later on when you have the cash and crossfire then. the motherboard has uefi and the case is a haf 912 like you asked. Plus shipping it will be about $30 over $700. you could get away with straight $700 if you got a board without uefi probably.
The 5400 RPM laptop hard drive would probably be suited as a secondary drive, not a primary.
I just tried making it as close to 700 as I could. If I'm not mistaken you can unlock the x2 phenom to a quad core also so I didn't see much of a difference between my cpu and the one you chose. I must of skipped over the SAPPHIRE when I was looking on newegg.