I just recommend a name brand like you listed there at 1600MHz (the highest fully supported speed for IB) with reasonable timings. Overclocking the RAM doesn't get you far in games - but there may be specific app software that benefits from it.
You should be able to get at *least* 4.2 from any Z77 board and a cheap cooler.
Is 32GB overkill? I was thinking either 16 or 32GB.