Jeff Nguyen says that dual Athlon workstations have become their best-sellers, beating out even 1U rackmount servers. ASL's dual Athlons are available with SCSI drives, with a RAID card and SCSI drives, or with the SCSI-less version of the motherboard and ATA drives. Jeff and his team are smart shoppers and careful builders, and they pay attention to things like getting ribbon cables out of the way to maximize airflow. Speaking of airflow, they're using a line of generic-looking but practical cases that put fan mounting points in sensible places, including by the drives, where you need them.
Another vendor is Monarch Computer Systems in Atlanta, a longtime custom PC maker but relative newcomer to the Linux hardware business. Monarch offers custom configurations, including an “Ultimate Linux Box” configuration in a sharp-looking full-tower aluminum case from Lian-Li.
The Lian-Li case comes with thumb-tightening fasteners for everything that screws into aluminum, and you should not take the thumb-ability as a hint but as a rule to live by. The aluminum is about as soft as very hard cheese, and the threads will probably strip if you say “screwdriver”. Monarch's box has good CPU and drive cooling, with two 80mm fans blowing straight onto a removable six-drive cage, two exhausting from above the video card near the CPUs and two above the power supply. Unlike some heavily cooled tower cases, all the air flows in the front and out the back, which lets you place it against a wall or another computer. When it's time to work inside the case, both side panels come off and the metal seams are rolled. All very nice except that the plastic feet and front-panel controls are somewhat cheap-looking.
Monarch's overall build quality is good, and the system survived some torture tests. I didn't have a chance to try their software load, which is a standard Red Hat according to their web site. The aluminum case is a big win if you want to move the system around or impress people; on a trip to the local installfest it was a lot lighter to carry from the parking lot than a steel case and also drew a crowd.