Putting together an upgrade from some used bits. I've bought an i5 2400, planning to fit a GTX960 or 970. Will play a variety of games and do the usual browsing/office/music tasks. The parts I've bought are coming with 8gb of DDR3, 2x4gb. I can get another two 4gb dimms or another 8gb dimm. Third option is just go with 8gb. Thoughts?