Upgrading PowerMac G5 to Hackintosh

Hi I have a late 2004 G5. Now I have called around about upgrading the guts to Intel Mac. No one could seem to help me..
My question here is what will this case fit? Is it possible to mount a Intel PC MOBO in this? Or will the newer Intel Mac Pro MOBO mount in it?

If Powermac processors were so great why did they go to Intel? Sounds like Mac wants to be more like a PC. Also how is it that AMD can be used if even the software calls for Intel Processor.

Hi I'm a PC, but I want the best of both worlds as cheap as possible.