I have the Beta bass 2X15 combo amp. The speakers have been replaced with carvin PS-15's (300 or 400 watt). Suprisely they sound pretty good consider how cheap they are. I may want to replace then again, but I'm not sure what to get. Head is built in, but removable with 4 screws. What I like about it is since the 1/4 inch plug is external, I can plug my Sonaro head into the cab and switch back and forth from tubes to SS. The Beta head is crazy loud. I usually play my bass through it. I have played guitar through it and it sounds great. I plug a tremelo and chorus pedal in the effects loop and use the gain for the fuzz. Actually, the beta bass head is in the shop, strange ac voltage coming out of the speaker inputs. So for now, i use my Sonaro head or play my Bassman 300 pro through the cab.