What type of ram upgrade should I get?

I have new intel imac 17" which I am thrilled to own. However, when I bought it I did not upgrade the ram or anything. The speed is excellent but I want to get call of duty 2 when it comes out for mac and I think I should probably add more ram if I plan to play it. So my question is... Is it better to buy another 512mb stick of ram and get duel channel power ( i believe the imac ram is duel channel) or would adding a gig stick be faster? I know that if you don't have two sticks of the same mb size the duel channel configuration doesn't apply. I know some people say more ram=faster but I'm not sure in the case of this duel channel stuff and whatnot... I mean, when I run a game it will just be the game running and OSX... nothing else. Otherwise the speed is fine for me just with 512mb.


and I just have to add this in... I LOVE THIS MAC! lol

Thanks in advance.

In the end, adding 1GB would likely be faster. Even if you add another 512MB and utilize dual channel mode, your hard drive will start paging do to only having 1GB total.