But - you *might* have more stable memory because of the 'reserve' not being used if you go for 1600...
I think even if it won't clock the RAM to 1600, it should surely run them at 1333 and therefore be safe. Under circumstances you might even get better SPD timings by that because the RAM won't be running at its upper design edge.
Gaming doesn't see any advantage from faster memory outside of AMD's LIano systems and the only reason they do is because the beefy IGP is bandwidth starved.
You could buy 1600MHz memory anyway because it is roughly equal in price to 1333MHz but it's unlikely you could get it to run above 1333MHz because that would require overclocking, something H61 chipset boards don't do. 1600MHz or faster emory should just be down clocked to the motherboards maximum, 1333.