What Bart said.
Re-use the case, but a new power supply would be good. The connectors have a compression type fitting and once taken apart from components, they tend to not fit very well. Unless you take every compression fitting and tighten them up ever so slightly with a needle-nose plyer.
I priced some goodies out on memoryexpress.com (In calgary but may be near where you live too). $764.
16 GB ram is only usefull in a 64 bit OS.
Code:
AMD A8-5500 APU 3.2GHz w/ 4MB Cache
$109.99
Asus F2A55-M LE Dual DDR3 1866, 7.1 Audio, Gigabit Lan, PCI-E, CrossFireX
$79.99
AMD MEMORY Performance Edition 8GB PC3-10600 CL8 DDR3 SDRAM Kit (2 x 4GB)
$99.98
Corsair Force Series 3 Solid State Drive SATA III, 120GB
2 PCS
$119.99
Asus GTX 660 DirectCU II GeForce GTX 660 2GB PCI-E w/ Dual DVI, HDMI, DisplayPort
$239.00
Corsair Gaming Series GS700 Power Supply
$114.99
This is just a quick sample what you can do. With this setup you should be able to get a 7.5 windows rating, which is pretty good. You could don't click me the latest and greatest $5000 computer and still not get over 9/10