Wanting to build a NAS

I wanted some advice on my first NAS project. I will be using WHS (I have a free copy) and I recently purchased the Modtek Alien X case (http://www.xoxide.com/xoxide-alien-x-case.html and http://modtekusa.com/index.php?page=details&id=1). In addition to the standard 120MM fan, I added an additional 120MM fan for the front and 80MM for side mounting, I wanted to be sure that the box stayed cool. There is enough room for 6 3.5" internal drives.

Where my questions are:
1) I need an ATX motherboard, I figured to get one with 6 SATA connections - can anyone recommend one?
2) I know there have reports of WHS stuttering on some of the Gigabyte boards, can anyone confirm?
3) When looking at what HDD to buy (I want to start with 1 TB) I know that speed is important but what other specs should I look at when evaluating drives?
4) I will be connecting this server to a Linksys Wireless Router (but thru wired ports). Should I buy a separate Gigabit Ethernet card to improve performance?

Thanks in advance for anyone's input. I will keep this thread up to date as my project continues.

Sorry for not including this information earlier:
Budget for CPU/MOBO: I would like to keep it under $150 if possible

Total Space: I want to start off with 1 TB and add on as I need to

Quick Data Access: Well I want to store my media files (audio and video) on the NAS, so I would say access speed important.

RAID: s far as I was reading with NAS, WHS doesn't support RAID and it has it's own disk extender (but again just from what I read so far)

^+1. Good build.

@OP: The $150 for just the board and CPU are fine. It won't cut it if you MUST get 6 SATA ports. HOWEVER, you CAN add in a PCI/PCIe RAID card. Perhaps around $200-240 for a good NAS with 6 SATA ports,etc.

Yes a m-ATX mb fits an ATX case. It just leaves a bit of space unused .

I was going to say b4 that if you use a RAID array then its safer to use a pci-e raid controller card , but they are not cheap .

I guess you could simply instruct WHS to make a copy on the other hard drives in the case . Once a day , sequential back up . So if there is a hard drive failure then you havent lost much if anything

most case fans have 4 pin molex connectors that plug straight in to the power supply .

Atom is very low power single core processor . If the NAS is just storage then maybe it would be OK , but Atom powered netbooks have trouble playing video so I wonder if an atom powered NAS can stream video .
You'd definitely want to check that with the people who are using them .

A while back Toms had an e7200 on a G31 mb and it was drawing 70 watts . The e5200 will be a little bit less than the e7200 since the architectures are fundamentally the same , and the clock speeds similar . Since its a dual core it will handle multiple loads much better