Sunn Amplifiers was established a few years before the SVT, and it started specifically as a bass amp company(the guitar models were an afterthought). Their first offering, the 200s, featured an unusual bass-oriented speaker cab(physically deeper than Fender's)loaded with JBL D-140 drivers, powered by a head that was derived from hi-fi audio. Eventually a more powerful rig, with larger cabinets, the 2000s, was issued and seen on all sorts of stages, usurping Fender's dominance.
Similarly, in the same time period with not quite as much in the way of sucessful results, but still serviceable, Kustom offered their solid state bass rigs with cabs designed to be low frequency friendly. Then Acoustic appeared with the revolutionary 360, still ahead of the SVT.