If you want one like the Sanus with the rollers under it on a track so it slides out and back into a pre-cut hole in the wall, Sanus does have a nice modular system.
Personally I used their Foundations series 36U rack that came pre-assembled, with the glass door on the front, shelving, blanking plates, etc.. and sits on casters, so it can be rolled out and back into place as needed.
Got that one on-line for under $800, with free shipping via trucking freight service, which is about half or less than a similar Middle Atlantic rack with the same options applied would cost (side and back panels, locking panels, glass door, 8 vented shelves in a variety from 1U to 3U, and blanking plates)
pics shown about 1 page back, I believe.