The MB150s has been my primary amp for rehearsals, trio, septet, big band gigs for several decades. Bought a second one for backup, still have it, but never needed it. Bought both used. I even have the GK extension that I occasionally use. The small rectangular shape (vs. round like AI...I have those, but don't like carrying them, hits my leg at a single point of contact), makes it a breeze to transport and carry. EB, EUB, and DB all work through it. I sometime use a separate preamp for double bass mounted on my stand connected to the effects return to use the GK as a powered speaker. It's serviceable and replacement speakers and parts are available from GK. I do recommend a slip cover or bag to protect it. I do have other equipment, but only when the venue requires more "push" (or feel somewhat guilty for having things that I don't use).
Even if I revert to the "dark side" of gasoholicism, I don't foresee parting with the GK MB150s.