Do note that it is rather tough stuffing many GPUs into a rig without any software/hardware issues. Some motherboards/drivers/os are known to be buggy and not display the correct/all of the GPUs in the rig. That said the RX400/500 series from AMD are great at Eth mining while the Nvidia GTX 1000+ series are the best at Equihash (ZCash, Zencash, etc)