Why would I need more than 8 GB of RAM in 64 bit Windows 7?

I know it's a bit insane, but I do a lot of multitasking on my current computer. I have three monitors and regularly run several dozen browser tabs, several browsers, voip aps, games, movies, Oracle VMs, xampp, adobe photoshop, and a lot more often all at the same time. My task bar takes up a large part of one of my monitors. I'm currently doing this with 6 GB of RAM and once in a while will max it out if I have a game open at the same time.

Does Windows 7 perform better with more RAM than it seems to be using now? Does it cache more or make use of it in a better way?