The difference between the 8 and 4 ohm rating on any amp will be minimal and barely noticeable in a band. What you [i]will[/i] notice is the number of speakers and, more importantly, the sensitivity of the cab.
I have a TH500 and use 1 or 2 Super Compacts. I reckon 1 SC with your TH350 would sound very good. This cab is pretty sensitive, which means your watts will make a lot more more volume so the 8 ohms rating shouldn't be the problem that you might find with other, less sensitive, 8 ohm cabs. The BB2 would also be a very good 1 cab solutions.
I'd give Alex at Barefaced a call and he can answer your questions.