As Reeece said...do not worry about it. I run AMD 9850x4 and have 59 processing going. I play all my games without shutting down a darn thing. It makes life less complicated OLC. Before and like you stated it was mandatory to shut down processes with a single core. Such pain in the butt. I love turning on the computer and just start playing. As far as having programs open, online, playing music, burning a CD, having a chat window open and on Teamspeak all at th same time without a hiccup...these machines can do it. I run 64 bit also. Probably the best move I made on this computer.
What is the craziest, having your AV running a scan in the background while you're online fragging some dude on the other side of the world and you do not even notice the AV is scanning.
After a few weeks of ownership of the new rig you will wonder why in the hell you waited so long to upgrade!