I gig regularly on both electric bass and double bass with a Carvin MB12. Great little amp. Value for money. I have an old small 1X15 ported cab with an old Carvin 15-inch driver that I run under the combo when I need the lowest 1/2 octave extension.
This replaced a Carvin PB300 that I used for 20 years on top of various cabs, including an SWR Triad and a Peavey 2X15 that I, again, loaded with a little bit of fiberglass insulation to cut down on cabinet resonance and Carvin 15-inch drivers.
And the Carvin PB300, which I still have and use as a backup with the SWR Triad and at the rehearsal venue, replaced an SVT head. About 1995, when I priced a re-tubing of the Ampeg, and it became apparent that the $$ I was going to use retubing would purchase a gigging power & quality head that would last for the next 20 years, the decision was obviated. Plus, the PB300 had a "new" gimmick: an XLR line out to the board, and a second "new" gimmick: onboard compression.
The new MB combos have all that and more. They deliver the power, tone, versatility and light weight at a fraction of the cost of the "boutique" amps out there. The only drawback is that the control panel is not as robust as the PB300 (I've had to send mine back for repairs from improperly loading it.