I considered one of them, but would've ended up playing "Whiter Shade of Pale" and then shrugging and putting it to one side.
I've got a Synth9 and a B9.
The Synth9 is really quite good and its Oberheim voice can provide a high sustained voice to accompany a chugging bass line, a bit like if you were holding a note on a MIDI pedal. It is also spot-on for playing "Subdivisions".
Similarly to the Synth9 and my comment re. the Mel9, I've found that one sound on the B9 grabbed my attention and I've stuck with it; it's great for playing "Lazy".
So overall, my thoughts on the range is that they are good for getting the canned sounds, but as per comments, they are flawed in that they don't go down to bottom-E.
I've also got a Markbass SS, which is very good at tracking, but doesn't go deep either.
And then I've got a Future Impact, which I've had a while but haven't quite got fully to grips with; my initial familiarisation and enthusiasm turned into solving a technical issue with it and MIDI and I ended up spending nearly as much again to solve it.