Corsair H50 is 540Kr on Netshop.no
H60 = 595Kr
H70 = 795Kr
Your options are limited on this one.
If you got a tripple channel CPU you can try with 2x2GB + 1x4GB. Seeing as you got an i5 CPU i would not recommend this. The reasoning for this is that the sandybridge CPUs are dual channeled. Meaning that they run best with 2/4 chips of ram.
You can stay with the stock cooler, viable option. But it wont be as quiet as an aftermarket cooler and your overclocking is pretty limited.
Or you can get a new CPU cooler aswell. Not neccesraly a watercooler but something that dont block your RAM slots.
Or get 2x4GB RAM and try to sell the old 2x2GB.