Just so you know-I kept a close eye when I was swapping back and forth between playing Rift and streaming the NFL draft last weekend..I got 16 gigs of memory and I was using 13gbs of it.
To be fair, I'm running a 1gb page file because I got 16gigs of memory, i had to up that to 4 gbs to get the memory to drop back down to 9 gigs.
What I'm saying is, if your gonna do some hard core gaming, you really can't be doing a whole lot else in the background. You can keep a few tabs on your browser open but not much else.
The whole reason I went with 16 gigs is because I used to run out of memory on 8gbs. Never had that problem with 16, last weekend was as high as I've ever seen it(first time I saw it over 8 gigs actually). So if you can get 16 gbs for the price of 8gbs on sale (like I did) I say jump on it and never have to worry about it again.
edit-I play 90% of my games on steam and I never came close to having problems...32gbs of ram is way overkill