Okay, so I've got my Markbass CMD121P, which I love. It gives me all the oomph I need for most venues. But not all. So I'm thinking of buying an extension cabinet. I have two questions. The first is purely technical. The power amp is currently connected to the 8 ohm internal speaker. I like the sound of this speaker and want to continue running it. Does this mean that using the second speaker output I should only run into an 8 ohm cabinet? Or can I take advantage of the full 500w by running a 4 ohm extension simultaneously with the 8 ohm internal speaker? Yes, I do understand the math involved in calculating total impedance when running cabinets daisy-chained together (e.g., single amp output into one cabinet and then into a second cabinet). What I don't know is whether the two outputs on the back of the Markbass head are the equivalent of a series or parallel connection... and I can't seem to get that info from the Markbass site (might help if I could read a schematic, but I can't). The second is utterly aesthetic. I would like to know what sort of results others with this combo have had with speaker configurations in extension cabinets. My lust for old-school 70's low end makes me think a 1x15 might be the way to go. At other times I think the combo might be improved with the added punch of a pair of 10's. Still other times I wonder whether mixing speaker sizes when the combo contains a 12 is a good idea at all (12's have a rather distinctive character that I happen to like a lot). Has anyone experimented with any of these combinations? Just FYI, I play fingerstyle "Americana," so no slappy-poppy for me... the tweeter in the combo is dialed back about 50% via the VLE filter, and I don't really care if an extension cab has a tweeter at all. Thanks Markbassers!