With regards to the rails, I'm guessing they are a pain to get / fit for a audio type rack?
Anyone recommend a good 4U case? Capable of holding ATX MB and 4 HDD's.
Compucase S411 - 4U, space for plenty of drives, and fabulous cooling. We've got six of these and they're absolute lifesavers. The innards are easy to access, the air routes through the case are well thought out so intake and exhaust fans can be set to low speeds, hence very low noise in operation. They also have optional hotswap bays for big RAID arrays. Wouldn't hesitate to recommend them.
As for racking them, all of ours came with rack ears, and we just screwed them into place like any other bit of kit. Lovely.
The rack is supported quite happily both by my freestanding Quiklok racks, and two of them in an SKB case. Yes they're heavy, but if they're for fixed installation then they'll be fine - I wouldn't want to go moving the SKB case around for example, as I expect that would probably be asking too much.
I have a Sun Microsystems server rack on the way which will have front and rear racks so at that point I'll fit them all with rails so they can be slid forward, worked on and then pushed back into place.
The fans literally clip in and out, so are a doddle to replace. We infact ripped out the standard ones and replaced them with a combination of Zalman and Papst fans to lower the noise threshold even further.
In our main workstation the right hand drive bay holds a DVD-R, a CD/RW and one hard drive, the centre as a floppy and another HD, and the left bay with the 120mm intake fan holds four HDs in a RAID array - they fit quite happily behind the fan mount and have the advantage of fresh air being constantly blown over them.
It's true the case are very deep, but this is a massive advantage in terms of usable components, standard ATX format PSUs and Motherboards, plus the easy route of airflow in the case.
Have a look at www.xcase.co.uk - they have a variety of shorter 4U racks, but you'll find they are compromised in terms of capacity and layout.
Sorry, misread your post a little..... I thought you were hunting for a shorter rack case, rather than realised you were after a deeper rack!
Any custom rack company will build you a deeper one if you ask them nicely. Cases like the S411 are designed for file servers and the like, where they'd be in industrial 24 inch racks - much wider than what we're used to - where the equipment is still only 19 inch, but there's space at the sides for fans, powerstrips etc. These cases are also much much deeper, plus they have the rear rack strip as well because when you're racking heavy servers and UPS, telco gear and the like they need the extra support. There are plenty on Ebay if you fancy one!
In fairness, if you're not planning on shifting it around much, I wouldn't worry - our two in the SKB rack stick about six inches out the rear, but it's only a temporary measure until the server rack appears. The ones in the freestanding rack are just that - freestanding!