With the cost of BTC slowly dropping, I think more people that mine at home & pay their own electricity are gonna start dropping out.  This will cause the diffifculty to go DOWN, like we saw a few months ago. Right now it's not the best time to build more mining rigs, but I built 1 simply because my main PC just crapped out and I need a new computer anyway.  Since I am doing that, I decided to spend the extra couple of $$$'s to make it a strong BTC mining rig