I went into a store a couple of weeks ago and tried out the rumble 350, if that helps. It sounded great, for my tastes anyway. The new Rumble's are Bassman technology, which were very well praised. I found it had a fairly decent amount of EQing options and the overdrive worked really well, I could select how much overdrive and then a separate blend knob, which really allowed me to get the slightly distorted sound I was looking for.
I think the 75's a bit of an odd number though. I guess it depends on what you're using it for though. If I were to use it to gig with, I'd probably get at least the 150, which also has a XLR output that you could plug into a PA. But the 75 could work with an acoustic and a keyboard or something. Just my thoughts... Hope it helped