After a few hours of trying to find a makeshift setup to at least try out the new Mobo, I decided I'd pack all the new stuff away until I could get a proper housing for it. Aaaaand. Now I can't power up the old Mobo.
My doubts about the quality of my computer science knowledge in the past 8 years is now at peak.
Cheapest full ATX case I could find is around $100 without shipping, and I wouldn't even know where to begin on a new power supply. I should go to bed.
EDIT: Got the old Mobo to work with the new GTX 650. On the first few benchmarks, it's performing roughly 2.5 times faster than my old card, and new features allows some software to run that previously wouldn't start at all. Yay for small victories!