building the value gaming PC

Hi, I'm interested in building the value gaming PC (>$1000), probably the athlon version, but I have a few questions....

I want this as mostly a gaming/surfing system I can network with my mac, maybe multiplay diablo II ect...

First off I have never put together a complete PC clone from scratch, I have upgraded ram and various cards, HDs etc., with no problem, but for the past 5 years I've used Macs, so all that is alot easier. Is it tough to configure the the bios & XP to recognize the different parts and get them to work together? OR should I just save alittle longer and buy a dell or other setup?

second: can I use the onboard sound on the MSI motherboard, or do I have to buy a soundcard to use most games? Are there any hidden parts I would have to get that aren't listed in the article, like HD/ATA/USB/Firewire controllers ect?

third: I would like a low cost router so I can hook up my DSL to both my mac and the PC, what's a good one that can offer firewall protection?

Should I go with the Athlon or P4, I'm leaning towards the athlon because I'm trying to do this on the cheaper side, and don't want to piss off the wife too much. (I figure if I can convice her that I put it together mostly from all the spare parts I have in the basement she might not be too pissed)

Any other parts/systems I should consider instead of what was listed in the article?

Specs according to article
Case: Antec SX 630 (maybe SX635)
Processor: AMD Athlon XP 1800+ or P4 1.6
Heatsink: Volcano 7 w/athlon shim
Motherboard: MSI Athlon XP KT3 Ultra or P4 ASUS P4S533
Memory: 256mb PC 2700 DDR (will 1 256 chip do or do I need sets?)
HD: 40 GB Maxtor D740X ATA 7200RPM
Video: Abit Siluro GeForce 3 Ti200
Monitor: (have one 19")
Soundcard: Soundblaster Live (do I really need this or can I add later?)
Speakers: (got 'em)
CD/DVD ROM: LG 16x DVD ROM
Modem: (DSL modem already)
NIC Card: D-Link DFE 530TX
Mouse: (got one)
Keyboard: (have Dell extended already)
OS: Windows XP Home OEM (what does OEM mean anyway? & how can I get it on the cheap?)
Floppy: any pana sony or teac disk

It all looks good.
OEM stands for Original Equipment Manufacturer, (the joke is that it stands for and more correctly Only Essential Materials)
If you want firewire connectivity you will have to buy a Firewire PCI card. And the USB is about the same thing.....except that there are already 2 on the board.
DDR can be installed with just 1 DIMM
I would wait for the sound card....as you don't want the wife mad.
Setting up the BIOS is a breeze, but you do want to take it slow.
XP is a snap to install, it will even format your drive for you.
:D
Hope this vague and quick reply helps