I used a single stage MBC, so I can't comment on the dual stage. My experience was that anything over 13 psi, the engine pukes (it's like hitting the rev limiter).
I've read on this and other forums that a BOV is a waste of money. It apparently doesn't do anything but make cool whooshing sounds. Don't know if that's true but if you do a search, you can read all about it.
I haven't seen a tri-gauge pillar pod for the Baja... If all you're going to do is add a MBC, then all you really need is a boost gauge. Don't get the Subaru model, which doesn't display psi but mA or something like that you have to interpret. It's no big deal once you get used to it, but why bother if you don't have to?