Currently, there are 30 GPU's in my farm total. 5 rigs of 6 cards each. 4 of the rigs are running Gigabyte R9-380's, 6 cards each for 120 MH/s per rig. I built one rig, using 6 of the R9-290/390 family that hashes at 180 Mh/s.
PSU's on the 380 rigs are EVGA 1300 watt Gold rated. PSU on the 290/390 rig is EVGA 1600 watt Gold rated.
All Asrock BTC H81 Motherboards, Celeron Dual cores, Powered USB 3.0 1x to 16x risers.
5 Dedicated outlets in my garage off the electrical panel. $0.10 KWh costs.
Very cool, honestly I think GPU rigs are probably the safest bet, very good warranties and a great resale on them. I mean look at the life of 7950, it launched January 2012 and it is still being used to mine. This rig could go on for a very long time if you need it to.
I'd have to concur on this one sir. My 7950's have paid for themselves over, and over again from back in the day, to now mining Eth. In fact, I just picked up couple more a few month ago. They are almost worth what I paid for them new $299 years ago.
$244 used on Amazon.