I can not see anything really worth upgrading except maybe adding a SSD, everything else is plenty for just about everything. It is a monster of a system.
Ahhhh very nice! You can definitely upgrade the cooler if you want, but you are ultimately just polishing an already solid setup. Have you considered getting into case modding?
im gonna agree with everyone else and say you got a pretty dam solid build their, but going to 2400mhz 2x4gb kit would do you so much justice dude, and even a pci.e x4 ssd (just cause it shits on sata) don't see any point in a cooling upgrade considering your already running a pretty boss system on a 4.5ghz oc
You should get a bunch of LeD strips and put them all inside your computer and desk and when you turn the lights off at night, your desk will look amazing.
SSD or two in raid 0 help lot with capasity and read and write speed, Liquid cooling block for your cpu something like Corsair H100i or H80i for more silence and finally going with crossfire ofcourse if you have PSU big enough for that. Going with i7 for faster video rendering speeds or something like that but not worth of cost you the computer is for gaming only.