So, much as I like AMD (have always had them since the Athlon X2 days) The fact that I've upgraded to a pair of 970s has left my 6300 hilariously CPU bound in basically everything. An upgrade to an 83XX would probably do a little bit, but ultimately feels like a bit of a dead end. So I've decided to upgrade to an i7 based system. Obviously X99/2011 would be the absolute best performance wise, but seems poor value.
Since it will be watercooled (along with the two 970s) it seems like the best value proposition is an OCd i7 4790k. However I have absolutely no clue about the types of boards that do well with these processors. Budget is around £100/115, although that could possibly stretched a bit if theres a compelling reason to do so.
Gaming Nics etc don't add anything as I use a discrete AC card, and it needs to be laid out for 3 slot GPUs in SLI as I may not go straight to WC on the GPUs. A quick look round indicates that the gigabyte Gaming 5 boards, or the MSI Mpower ones are probably a good choice - can you really go wrong at the £100 price point?