Alright, good news! My parents are buying my brother a new computer for Christmas, so I will be using my HP case and HDD for the new build, which saves me a good amount of money.
Right now i've got a cart on Newegg (all those sales on Amazon that made half the items cheaper were apparently a one-day-only thing), containing the items you linked for the build with the Intel processor, and with the GPU you linked in your last post. With a copy of Window 7 added on it totals $645.94 ($759.24 with shipping and taxes included), so it's pretty well right on budget to!
I was hoping to work out the cost to $700 with shipping and taxes included, but I have a paintball gun an old friend will buy from me at a moments notice that will cover the extra plus some. Considering that, I considered looking into a cooling unit as well, but I can save that for later if I end up wanting / needing it.
The last thing I can think to ask right now, is if there would be a way for me to swap in the new Mobo without having to format my HDD. I don't know if such a thing would be possible, but it would save me from having to buy a copy of Windows 7, as my PC already has it installed, and if a method exists you probably know about it. It would also bring the benefit of not having to reinstall all of my games and software, and I wouldn't have to worry about losing any of my files.
I'm excited to see this actually come together.