I have a rig for sale that's plug-and-play ready, just add the GPU's of your choice, and mount them as desired (can theoretically fit up to 7 with additional power supply). I was running 4 R9 280x's on this rig at 2.85 MH/s.
I have:
Power Supply: Corsair 1200 Watt Gold PSU (AX1200)
Motherboard: MSI 890FXA-GD65 (7 PCI-e slots)
Processor: AMD Sempron 135
Memory: 4GB DDR3
HDD: Seagate Barracuda 320GB
Risers: 4x 1x-16x PCI-e
ribbon Risers, and 3x
USB 1x-16x Risers
*60cm* (not pictured)
Windows 8.1 with CGMiner, GUIMiner and CGWatcher installed.
Price includes shipping via USPS Priority 2-day within the US. Additional charge for international chipping.
Asking 1 BTC OBO (or USD 650 via PayPal)
.