The difference between 1866 and 1600mhz RAM in rendering and encoding is so small you can't even feel it. Sorry you are wrong here.
You do not need a platinum PSU for this build at all. there are a ton of JUST AS HIGH QUALITY bronze/silver/gold units that will be perfect and save $70.
There are TONS of boards with all that stuff for cheaper. They are all over. The SABERTOOTH is all marketing.