PCPartPicker part list: http://pcpartpicker.com/p/3lnSA
Price breakdown by merchant: http://pcpartpicker.com/p/3lnSA/by_merchant/
CPU: AMD FX-8320 3.5GHz 8-Core Processor ($151.99 @ Amazon)
Motherboard: ASRock 990FX Extreme3 ATX AM3+/AM3 Motherboard ($89.25 @ Newegg)
Memory: Kingston Black 8GB (2 x 4GB) DDR3-1600 Memory ($64.99 @ Newegg)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($57.99 @ NCIX US)
Video Card: Sapphire Radeon R7 265 2GB Video Card ($167.27 @ TigerDirect)
Case: NZXT Source 210 (Black) ATX Mid Tower Case ($29.99 @ Newegg)
Power Supply: Corsair Enthusiast 750W 80+ Bronze Certified Semi-Modular ATX Power Supply ($84.99 @ Newegg)
Optical Drive: Samsung SH-224DB/BEBE DVD/CD Writer ($14.99 @ Newegg)
Operating System: Microsoft Windows 8.1 (OEM) (64-bit) ($89.98 @ OutletPC)
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-04-03 14:46 EDT-0400)
Best I could come up with. If you are near a Microcenter you can shave off $30-40 and fit a cooler in there. Overclock and SLi/Crossfire capable with OS+various bits it a lot to ask out of $750.
You need to decide if you want the best you can get out of your $750 now, or something that is high-end-ready with a placeholder video card. This build is leaning towards the latter.