Re: Xotic BB Preamp
BB Pre sounds great. Nice way to add clean punch, or to kick your amp's front end "night in the ruts."
I've used the EP Booster the same way. It has a subtle eq curve (selectable with internal switches), and can really add a nice bit of gain for solos. Also sounds great as an always-on tone enhancer.
I have no experience with their other boosters, but seeing how awesome the other Xotic pedals are, I would not hesitate to pull the trigger if I found them somewhere.