Hey Mouse-funny you should mention this I just got back from doing the same....
I toured around the last couple months with a 4U rackmount PC(Asus P4PE/2GHz/512MB/removable HD's) in a big SKB shockmount case-
http://www.skbcases.com/product/pro_aud ... -904u.html
-this was essential and I was only travelling through Canada and the upper midwest states-for international these cases are a must!!!
ATA flight cases are damn expensive!!
The rackmount computer case itself is:
http://store.compute-aid.com/cgi-bin/ca ... type=store
It's super heavy duty steel, and since i've been a lurker here for awhile
I simply applied all I learned here...quiet power supply(Zalman 300w) and a Vantec Stealth 120mm intake fan, Zalman 6500 flower cooler and a fanbus for the fans. The case is big and has great airflow, but I had to mod the back to get a couple of 80mm fans in there. I also lined the entire inside of the case with thick neoprene mousepads.
Anyways, a bit of DIY and I saved tons, but if yer gonna get it done for you, even better. I did FOH sound and recorded bands on 16-24 tracks at 24bit/44.1kHz with 3 Presonus Digimax's and an RME Digiface(with a Lucid Genx6 Wordclock) and it performed flawlessly for a month on the road.
The 4U steel case inside the shockmount SKB case was heavy, but worth it as I could put it in with all the rest of the gear and not be worried about it.
I'm selling the SKB shockmount case if yer interested, I've got 3 months of mixing to do then i'm off for a few months on a different project and won't need it again.
Email me if yer interested-I'd do it for $180 USD(retail is $350-$500USD)