right off hand the first thing that comes to mind is the psu, make sure it has the right connectors/rails.
second, you probly wont see an improvement with a higher speed ram. i would get a GOOD 1600mhz with a good xmp,
ssd's in raid will be faster, but as far as gamimg only a slight gain. loading stuff->FASTER. we are talking seconds, they are faster w/o a raid too.
keep in mind your internet speed if your mowin fools down online, a $2500 computer wont compensate for crappy internet speeds....mmm thats just my opinion.