Parting out the components would probably
be best. Your budget and needs
will determine what you should sell or reuse. Maybe this should be in the Help Me Buy/Help Me Build section. A new i7 and mobo wouldn't cost you much. If you game a lot you might want a new video card or maybe you can wait a little longer.
Some of the folders
might take the CPU, mobo, and Video card off your hands. You could probably
get access to Team MPC - Hardware Swap & Sell.
I'm not sure what people would pay.
What case are you currently using?