Would I be better off buying an i3 2100 and a 6970(or similar)?
As far as a case goes try something like the Arc Midi from Fractal Design. Have heard plenty of good things about it and has great cable management. and regarding your processor, if you are going to step down to an i3 please consider a used cpu and motherboard with an older socket. Even though it may be a gen or two old older, you wont be loosing the power of the older processor but add on features like integrated graphics and ssd caching. try looking at craigslist and see what you can find.