This is a decent idea. My brother built a similar rig, and he plays a lot of newer games on high settings with it, including Skyrim with mods. The A10 5800k is definitely a very good APU(CPU + GPU) for the price. The built in GPU is a Radeon 7660D, which is good enough to run most games on mid to high settings. Decent enough rig to run PCSX2 or Wii games on Dolphin.
PCPartPicker part list / Price breakdown by merchant / Benchmarks
CPU: AMD A10-5800K 3.8GHz Quad-Core Processor ($129.99 @ Newegg)
Motherboard: Biostar A55MD2 Micro ATX FM2 Motherboard ($55.97 @ Newegg)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1866 Memory ($68.99 @ Newegg)
Storage: Western Digital Caviar Black 1TB 3.5" 7200RPM Internal Hard Drive ($94.99 @ Newegg)
Case: Apex PC-389-C ATX Mid Tower Case ($38.98 @ Newegg)
Power Supply: Rosewill 350W ATX Power Supply ($32.98 @ Newegg)
Optical Drive: Lite-On iHAS124-04 DVD/CD Writer ($14.99 @ Newegg)
Total: $436.89
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-05-17 01:16 EDT-0400)
Another positive is you aren't buying OEM junk with Windows 8 pre-loaded.
The PC part picker is useful for finding deals, so occasionally you can get better deals on specific parts. But you might have to look around. Also, there is no point in using the microcenter price if there isn't one anywhere near you. but they frequently got great deals, especially on combos for mid to higher end stuff. Combo deals are something else you might want to check out. You could get a better quality part for about the same price or a little cheaper than without it.
For closer to $500 you could build a rig similar to this which is quite a bit better than the above rig. And you could play mid to max setting @ 1080p for a lot of games:
PCPartPicker part list: http://pcpartpicker.com/p/ZXND
Price breakdown by merchant: http://pcpartpicker.com/p/ZXND/by_merchant/
Benchmarks: http://pcpartpicker.com/p/ZXND/benchmarks/
CPU: AMD Phenom II X4 965 Black 3.4GHz Quad-Core Processor ($79.99 @ Newegg)
Motherboard: Asus M5A97 LE R2.0 ATX AM3+ Motherboard ($68.99 @ Newegg)
Memory: Patriot Signature 8GB (2 x 4GB) DDR3-1600 Memory ($49.99 @ Amazon)
Storage: Hitachi 500GB 3.5" 7200RPM Internal Hard Drive ($54.99 @ Newegg)
Video Card: XFX Radeon HD 7850 1GB Video Card ($149.99 @ Newegg)
Case: Apex SK-393-C ATX Mid Tower Case ($32.98 @ Newegg)
Power Supply: Corsair Builder 500W 80 PLUS Bronze Certified ATX12V Power Supply ($49.99 @ TigerDirect)
Optical Drive: LG GH24NS95 DVD/CD Writer ($14.99 @ Newegg)
Total: $501.91
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-05-25 17:10 EDT-0400)