Another, older configuration that I came up with. May have some compatibility issues...
Here are the basic specs:

AMD Quad-Core 3.0 GHz CPU
500GB HDD
8GB RAM
WLAN Wifi (single; not dual)
AMD GPU

Total (give/take $10): $260

Here are the parts:

-HDD (30):
http://www.provantage.com/dell-469-4180~7DELL2QM.htm?source=googleps&gclid=Cj0KEQjw7b-gBRC45uLY_avSrdgBEiQAD3Olx99N4m21cOLskwsl5_rR6UXqighbDezl4cQOrTe_gaIaAkMz8P8HAQ

Network Card (12):
http://www.newegg.com/Product/Product.aspx?Item=N82E16833704060&cm_re=pci_express_network_card-_-33-704-060-_-Product

RAM (50):
http://www.newegg.com/Product/Product.aspx?Item=9SIA0ZX1926685&nm_mc=KNC-GoogleMKP&cm_mmc=KNC-GoogleMKP-_-pla-_-Electronics-_-9SIA0ZX1926685

Power Supply (40):
http://www.newegg.com/Product/Product.aspx?Item=9SIA30R1MP3648&cm_re=micro_atx_power_supply_500w-_-1HU-0026-00003-_-Product

CPU (63/80 - you can choose one):
http://www.somenit.com/AMD-FD4200FRW4KGU-FX-4200-Quad-Core-Processor-3-3GHz-Socket-AM3-OEM-BG01580?find=ok

http://www.newegg.com/Product/Product.aspx?Item=N82E16819113369

MotherBoard (50):
http://www.newegg.com/Product/Product.aspx?Item=N82E16813157292&cm_re=ASRock_AMD-_-13-157-292-_-Product

Case (13):

http://www.provantage.com/antec-vsk3000e~7ANTG07X.htm?source=googleps&gclid=Cj0KEQjw7b-gBRC45uLY_avSrdgBEiQAD3Olx1gI-UQu1qsy4_FM1klDXdXkOsU9g84Yg2gtVgfi_O0aAq-V8P8HAQ