Don't buy the i5-2300. It's a 2.8GHz CPU for $185, while
i5-2400 is a 3.1GHz CPU for just $5 more.
Since you don't seem concerned about crossfire/sli capability and your CPU is not overclockable, you could save some cash by going with a H67 motherboard. You won't miss SSD caching (= Intel SRT), which is really the only advantage you'd get with Z68. Here:
Intel BOXDH67BLB3 $81 after promo (has Intel's network controller which I hear is superior to the more common Realtek chips).
Definitely
do not buy a 5400RPM hard drive as your main drive for OS and programs. Bad, bad idea. How much space do you think you'll actually need in the immediate future? Is
500GB enough? Hard drive prices are bound to fall to normal levels sooner or later, so try not to spend a lot on storage if at all possible.
I'd buy this 6870 over the Sapphire:
XFX 6870 $145 AR. Transferable lifetime warranty, free shipping - same otherwise.
You'd save about $100 with the cheaper mobo and HDD combined, enough to afford a 64GB SSD or a 6950 2GB.