Unless you need to keep in touch with all of your internet buddies via steam because all of them will assume you've been hit by a truck while you're away or you enjoy playing the witcher and minecraft at the same time, there is no reason to keep steam open. it's like running your radio in your car while taking a stuff in your bathroom.
6 gigs of ram not enough? Sir what the forget is wrong with you
I have 4 gigs of ram, Minecraft only needs two and that's being generous. I run two monitors, with Skype, Steam, Mumble, Winamp and Chrome (which generally has six to eight tabs open
at least), and I don't suffer any performance hits for it even on far render distance.
If you're having performance issues with Steam and Minecraft running at the same time, maybe you should stop whining about your memory and consider getting a multicore processor.
