Soldato
I have the Phantom Spirit Evo and I can confirm that you can indeed raise the fan to give more clearance on the RAM if needed, its just a couple of springy wire doofers that you can slide up the cooler a bit, sorry for getting all technical there.With the peerless assassin, I believe you can raise the right fan a bit to give you more RAM height clearance, since the phantom spirit is so similar I assume you can do the same, but I don't know.
I wouldn't waste a slot on a small boot drive, especially since small drives tend to be worse value (500GB can be terrible value).