I've had the B3n only 24 hours, but it's pretty similar to the B1on, and it's perfectly possible to get reasonable synth tones from that. What is trickier is really punch sounds. Triggered PWM sounds have rarely been good. The Behringer Bass V-Amp is still one of the leading options, and I need to decide if I am going to now sell one or both of my V-amps (having the space back would be good, and an extra £30). The Pod XT can go, though, as it doesn't really offer much over the B1on/B3n, apart from the potential for MIDI control as part of an automated setup for other effects on other instruments.
Some of the explicit synth sounds are a start, but they are sometimes a bit raspy, so you need to trim them with EQ, and some chorus afterwards helps. Using the traditional grouping of compression, octave, overdrive, filter and modulation works well, and you can be flexible with ordering. I managed to get some pretty good sounds even out of the B2 or B9, and you have much less flexibility about combinations of octave, filter, and ordering there. (E.g. sometimes you don't have an octave left, so have to use pitch shift, but then lose the option of chorus).