What about this:
HP ENVY Intel Core i5 3.0GHz Desktop
It's Factory Reconditioned HP, and it needs an update to the PS (and I've heard that HP Envy PS's aren't custom) and graphics card, but it's $500 for:
Processor: Intel Core i5-4430 3.0 GHz (Turbo up to 3.2 GHz)
6MB Shared Cache
Processor Core: Quad-Core
Memory: 8GB DDR3
Max Memory: 16GB
Memory Slots: 2
Graphics: Intel HD Graphics 4600
Hard Drive: 2TB SATA (7200rpm)
Optical Drive: SuperMulti DVD Burner
Audio Codec: Integrated IDT 92HD65C
Sound: 5.1 channel
Network: 10/100/1000 BASE-T
Wireless: 802.11a/b/g/n/ac (2x2)
Bluetooth: Yes, 4.0
Power Supply: 300W
Has 4 USB 3.0 spots, a 15-in-1 memory card reader, 6 USB 2.0 spots