I am also surprised that there aren't any smaller amps with built-in biamping. By the time you add a second micro-head and even that little Rolls crossover, or a rack preamp, you might as well get into a biamp friendly "full size" head like the old Peavey Megabass (edit: so as to not mislead, it's a 2U rack head).
The MB is cheap used and I'm having a lot of fun with mine. But even though it's class D (early class D), I would not categorize it as light (about 30 pounds). It's still about as portable as the MB-1 + class D PA amp sort of solution and at least you don't have to have a rack, necessarily, to carry it around.
It's an affordable and certainly effective option if you just want to play with biamping, at least.
Last edited by lossfizzle : 08-22-2013 at 07:34 PM.