myrison,
a 600 AND an 800? Damn, that must be a wild ride!
Actually, I've had the 600 unplugged almost since I received the 800. I have a second/third sub in the back of the room (an Earthquake sub) that does a very nice job of evening out the sound in the room.
I wasn't able to integrate the 600 very well with the 800/Earthquake and just gave up tweaking it because it sounded great with the 800 + Earthquake.
I've been toying with the idea of selling the 600 but there doesn't seem to be much of a market for reselling a big expensive sub like that, so it just sits in the corner and looks nice for now.
Jason