Linux server for home. Opinions wanted!

I am looking to build a linux server for home, and would like opinions on what components to use. My budget is $2000 and the server will run the following services:

Firewall/gateway to the Internet
File/print server
e-mail/web/ftp server

I have good experience running the Mitel Networks SME server (based on Red Hat, see (www.e-smith.org) on an older machine for a couple of years, and will use that OS for the new server as well.

Usage will mainly be serving mp3 and DivX files, so I am planning to get lots of storage.

I will use two smaller HDs running raid 1 as the system disk, and four large IDE drives in raid 5 configuration for data. Since raid 5 capable hardware controllers are out of my budget, I will use software raid.

My preliminary shopping list is as follows:

Chieftec UNC-410S rack mount case
ASUS P4B266 mainboard
Celeron 1.7 GHz
256 MB PC2100 DDR ram
2 Promise Ultra133 TX2 controllers
4 Maxtor D540DX 160.0GB disks
2 Maxtor D740X 40.0GB disks
2 3COM FAST ETH. 3C905C-TX-M
Any AGP graphics card, DVD-rom etc

The two Promise controllers make 6 IDE buses in total. I want each HD to have its own bus for performance and security reasons.

I'm fairly clear on the storage side. My main concern is what type of chipset, CPU and memory to get. I am a bit hesitant towards AMD for this machine, since heat will be a big concern with all those disks. How heavy is Linux software raid on the CPU? Is the Celeron 1.7 overkill, or do I need even more? I guess the network will be the big bottleneck, but I'm not sure.

All input is greatly appreciated!

On the internal network, there will be my PC, my wife's PC, the living room DivX PC and an Audiotron. External access is almost nothing.