Years ago I had a cabinet made by a local woodworking firm.
The advantage is that you can dictate the cabinet size to fit your room and system, but it will not necessarily be the right size for your next upgrade, therefore infinitely adjustable shelf height is mandatory.
Mine was designed so the rear panel (with holes in for cables etc) could be removed and the cabinet still retained its integrity. The holes for cables and plugs were a pain to use and forced cables that should be kept reasonably separate ie. mains and signal cables, to be almost bundled together, so now the back panel has been permanently removed.
The top of the cabinet extends at the back, so its the first thing to touch the wall when pushed back into place and avoids skirting boards etc, but also leaves space for cables to mains sockets, and don't forget a cable cutout if equipment is to be located on top.
Mine has wooden doors to hide all the boxes but as my system grew the distribution blocks now sit alongside because foo cables and blocks will not fit inside!
One thing to remember - when changing amps etc it is a real pain pushing cables on the back and also trying to hold the box from the front, really difficult. However, I like shutting the doors and hiding stuff, keeping dust at bay, so although I have permission from swmbo to have an open rack, it is somethin I will avoid as long as possible.