Ok, I was wrong. :P

Mine is set to Miles Fast 2D.

But, for all my slaves I have the following turned down to the lowest settings in Optins -> Sound -> General:

1. Sound Variations - "Reducing this setting will save memory at the cost of sound variety."
2. Max Simultaneous Sounds - Lowest setting is 8 I think.
3. Max Footstep Distance - 0.0

I'm going to dig through some other stuff.

I haven't really been having any problems with running 6 instances on my machine. I have my main window set to run with almost every setting at max.
There are a few things I turn off because they just annoy me (insane ammounts of grass/plants on ground). But it can't hurt to find a way to turn the sound off on the other 5 since I don't use it anyway. :P