Should I upgrade? if Yes, what?

[jamesbay]

I have similar spec on my computer and the best upgrade I did was getting a 250gb SSD HD for my main drive and 1tb SATA for storage. The SSD disk is really nice, no noise and super super fast!

From the manual it says your MB supports 24gb RAM. Since you are from Denmark I take it you know Edbpriser. There you can find 16gb RAM for a bit less than 700 DKK (92 EUR), so this would be a really cheap upgrade.
Jetway - Tech.On The Move - Motherboard - BI-600

Edit: Do you run OS X Lion? It does not hurt to have a decent amount of RAM if running multiple instances of WoW. I sometimes use 12gb out of 16gb when running 5 WoW instances. I believe it is because OS X does not clear the memory, but just keeps it inactive so that the programs you have recently run will execute fast.

[JoshDylan]

I must say, you have a nice rig. Ill have to post mine one of these days.

[Killadamo]

if you fully want to build a new rig, i suggest something like this
Intel Core i5-3570K, EVGA GeForce GTX 660 Ti, Xigmatek Elysium Silver - System Build - PCPartPicker Australia

It's in AU prices as i'm from Australia