ive got that same overhead console in my 93 chevy k1500, they are help up from the visor brackets, i guess if you found one that fit in the Xterra you could fab or get a bracket that would mount in between the visor and the roof and itd work.
also mounting it to the visor mount might seem weak but mine doesnt move at all, i wouldnt suggest getting that middle thing though, all it does it add a change thign and a place to put sunglasses and mine moves around a lot, like theres a space between it and the ceiling so it isnt flush, im sure if you wanted to though you could figure something out to make it fit good but i dont think its worth getting the added middle thing, just the rack is pretty handy, ALSO(this is the last thing i say dont worry) you might wanna replace the carpet that is on the inside of it, when you put things up there i.e. cell phone, cd's, etc they tend to move around and sometimes when you accelerate too fast theyll fly right off and hit you in the face
