I use my Weber's line out to go directly to the home stereo (with my bassman 50). I do not even have a speaker plugged in so I expect it to sound different than with a speaker. I must say that I read a lot of positive things about these Weber's with a speaker motor in them. And most important: I am happy with it.
@Iron Fist: Do you happen to know the differences between an MF280 and a MF280L cab (apart from cosmetics/looks)? What ohmage does your MF280L has?