I just cleaned things up a little, but the only surfaces that should have welded points are the trim around the screens, and the inset areas (not the flat back piece, but the actual inset areas - I welded those points so they would smooth correctly inside the corners). If anything else is welded, I need to correct that - I just uploaded an updated version with the vertex corrections to ShareCG. That point above where the gray outer surface meets the purplish inset should not be welded between the surfaces - there should be 3 separate points: 1 for the inset, and one for each facet of the outer gray surface; that's how the model currently stands.

What troubles me the most is the smoothing artifacts I continue to get on the flat uper floor surfaces; those polys are all split, from each other and from the gray vertical surfaces, but I keep seeing smoothing artifacts along the edges between some of the polys, and where they meet the corner of the gray facets. Yeah, it's driving me a little nuts ;-).