My Little farm is only 2 PCs for now. The First is a HP Z800 Workstation with 2 Intel Xeon X5672 3.20GHz quad core hyperthreaded cpus, 24GB of DDR3-1333 ECC Registered memory, and a Reference GTX 970. This one is Running full bore when I'm not using it and it gets an average of 235802 ppd.
The Second is running light because its my HTPC/NAS so I don't want to overwork it while we are trying to watch movies or stream stuff. Its a Phanteks Enthoo Pro Case, Gigabyte GA-P43-ES3G Motherboard with a Xeon X5450 3GHz quad core cpu, 8GB of DDR2-667 memory and a Asus Radeon HD-7790 2GB Graphics card. This one is only averaging 2680 ppd because I have it on the lowest setting because its pretty much used 24/7 for other things.
I plan om adding more eventually.