I can't recommend P-Link cases enough... for several reasons.
The biggest reason is they have REAL WORLD PRICES. Apparently, Rackmount PC cases = Industrial = Servers = Corporations = Big Money.
They also seem to have a lot of rack cases with shallower depths! Considering the typical rackmount PC case is a whopping 22" or 24", this is something to look for.
Keep in mind that IT Engineers at big companies don't care how Big, Loud or Heavy a case is. Us musicians come into THEIR world caring about these things.
To my knowledge, there is no such thing as a "quiet" rackmount case. What I've seen from a lot of companies like Sweetwater, ADK, etc is that they'll put sheets of roam/rubber acoustical material on the insides and replace the noisy front case fans with nicer Noctua (or equivalent) case fans or better yet, remove them completely (they tend to be over ventilated anyway due to large, hot server racks).
Another thing: Buy an Aluminum rackmount case. If you have not yet picked up a Steel 4U 24" deep rackmount case, PLEASE trust me... you don't want to go there.
I have spent a total of many weeks scouring the web for the best DAW rackmount case and have found nothing that compares to this:
http://www.plinkusa.net/web3035s.htm It's lightweight enough to easily work with, Doesn't have any %&^$ doors that always get in your way (I've had two of those), An inset power switch you won't accidently hit. shallow enough to not need some special roadcase for it. I've built 3 systems with this case and love them!!!
Keep in mind that, with this case, if you use a full-size ATX motherboard you will lose the ability to fill the bottom 5.25" bay. There are so many great micro-ATX boards that you shouldn't have a problem.
CakeFan
PS - I went out to the local electronic store and bought a single-pole 12V micro-switch that fits right in one of the square holes of the vented face of this case and wired it to the front fans so I could cut them off during recording. BUT HONESTLY, I don't think this case needs front fans... it's well ventilated anyway. Good Luck!!!