I use this computer for mining Litecoin. The 3 R9 270s work well and get me about 495khash/sec each.
I do believe that getting the HX850 PSU was a bit overkill. I probably should have gotten the HX750 for $30 less. The ASRock H81 Pro BTC motherboard was a good choice. It was cheap and good quality.
In total, I spent about 7 hours putting this PC together. It was a good experience.
The amount of crypto currency that I am getting won't get me to break even unfortunately but it was still a good experience. I might not be getting much out of it but it was a good experience to build this computer.