I have the Triton combined bobbin/belt sander, got it for about £160 odd. It's "ok", better than nothing, but it's not great. I found it doesn't do either function particularly well. The belt has a bit of a wobble at top of stroke, the largest bobbin size is pretty small.
I previously had the Triton standalone bobbin sander (think it's about £120 odd now) and that was very good. I was pretty happy with that until I broke it doing something stupid. Seeing as you already have a belt sander I'd go for a standalone bobbin, gives you more money to chuck at a bandsaw.