Hi.
+1 to the rewiring to be impossible.
+1 to the impedance switch.
I'm a fan of Marshall guitar amps with bass, but if 50W is really all You need, running a 100 watter with two tubes is much better option.
OTOH, if Your guitarist and drummer can play quietly enough for you to keep up with the 1987x, hang onto those guys

.
Regards
Sam