Remember the i3 isnt a quad, its only a dual. The cheapest quads (IIRC) are the Athlon II X4s.
Games like BFBC2 and COD:BO use a lot more of your CPU cycles than previous games so it is starting to become more common however unless its bang up to date games your playing on you wont really need it. Seems odd that you would be thinking of it anyway as you already have a PS3 and a seperate gaming machine, what do you see yourself playing on the HTPC?