No idea what you want to spend, but the cheap E5-2670's and friends have driven up the price of used X79 boards something silly. I found a new Supermicro X9SRA or ASRock Rack EPC602D8A to be much more palatable (both are still available new). Sure, they cost a bit more than a used X79 (not that much though), but they're new with a warranty and you can stuff them full of used RDIMMs from eBay for cheap. Like 8x8GB DIMMs of Registered ECC DDR3-1333 for ~$120 (total). If you don't already have RAM for an X79 board you should come out way ahead.