i have a GK microbass amp, and i swear by it. there is a single 12" speaker, 100 watts, etc. here's a link:
http://www.basscentre.com/bass-combo...ies-combo.html
there is a lot of power here - more than enough to play over the drums and fill a room. also, i tune in fifths so i've got a c below e that rumbles like you wouldn't believe out of the GK. although my preference lies in 2X10" speaker size, the portability and power of this little guy impresses me every day!
ps: it only weighs 26 lbs!