Seriously mate, the Monolith Magma is the way to go. It's definitely not "just" a bass amp. Guitarists and bassists have generally used the various Betas interchangeably, and the Magma is no different. I'm primarily a guitarist, and I ordered a Magma. If you can live without onboard reverb, the Magma is ideal.
And, really, the biggest reason I advocate for the Monolith is a practical one: All of the Beta units are thirty or so years old, and no doubt some of them are reaching the end of their useful life. I'm sure there are plenty of Betas that will continue to kick ass for another decade, but considering the hassles associated with servicing solid-state gear, why not get a unit that will operate hassle free for years to come?
Just my two cents, and good luck either way!