Upgrade help

You will need a p67 or z68 motherboard for the (K) processors. H67 will work too but has very little OC capabilities & the the (K) processors are MEANT to OC.

Ram is fine can upgrade to 8gb if you want

HD will work

PSU: What GPU are you using & do you plan to upgrade that too?

Right now i dont have a GPU, but im looking at getting the Nvidia GeForce GTS 450(or 440 can't remember)
well how about the 2500?

it will work with no problems whatsoever, the 2500K will work fine in a H61 mobo, and will turbo boost to 3.7 Ghz also, you just cant overclock further than that unless you go p67/z68.

as for the GPU i would definetely go for a ATI 5830 it has a 30% performance gain over the GTS450 for the same price (cheapest gts450 vs the 5830) although it is slightly longer:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

What do you use your computer for? For games/general use, your 2100 will be fine with a gts 450.