Servers can be really expensive. Your requirements have to be based on how many hits you get and how many users try to access the computer at any one given time.
Several computer manufacturers are making desktop motherboards with Gigabit Ethernet integrated into the motherboard (This allows more bandwidth for network connections with multiple users). Dedicated server boards can be dual or quad processor boards and have support for the longer gigabit ethernet slots and extra support for 2-20 gigabits of memory depending on the motherboard. I saw a setup on a quad Xeon system running about $10,000.00. The cost comes from a really pricey motherboards with SCSI Drive support and a really large redundant power supply (700w). This was for a RAID system with 4 SCSI Hard Drives.
I Saw a nice 4U Rack Quad Xeon at
You will have to read the Specs to appreciate the Price. It is a radded out server on steroids.
Alternatively you could buy a cheaper board that just supports dual PIII processors. Maybe a TITAN Motherboard.
Another alternative is to use a one Processor Motherboard and purchase the fastest processor available and use a RAID PCI card and use a couple 120 Gig Western Digital Special Edition Hard Drives with 8Meg Cache for Speed. These drives are almost as fast as SCSI but run on an IDE ATA 100 interface. You could run them in parallel to back up the data or run them using striping to gain more speed.
Another alternative is to just purchase a Dell Server. The entry level servers don't cost too much. The advantage is that the case is designed to hold up to 4 drives and can handle at least 2 Gigs of RAM.
If you have lots of RAM you can put a Database in Memory and acheive higher speeds. The trade off is high capacity Error detection/correcting RAM is expensive. I think a 2 Gig DDR Ram DIMM is like $2000.00! Using a single DIMM increases the speed of the RAM. The New Granite Bay Chipset Motherboards use DUAL DDR. You have to add RAM in pairs, but you could easily buy Two 512 Meg Sticks for 1 Gig of RAM and the Memory Access is faster and support the P4 virtual Multi-Threading Processors at about 3 Gig Processor speed.
A good Tape Backup or some way to back your system up may be nice also. If you do not like my post feel free to point out your opinion or my errors.