The very first thing I do is to run AIDA64
with all options for 48 hours straight before I install anything besides the OS. I am a hobbyist system builder so I want the components to fail ASAP -- that is if their going to fail, hopefully not. Next, Memtest overnight. Double ALL that for a Workstation.
As far as DDR3-1333 vs DDR3-1600 it depends upon the kit.
Q - What exact kit? ; please provide a link