I just finished building my first WHS using OEM builders software and a Gigabyte M57SLI-S4 motherboard. It is a board that I had around from an upgrade and is around 2-3 years old. It uses an NVIDIA chipset with an NVIDIA gigabit ethernet adapter.
I am using it with a dual core Athlon, 1 gig memory, SATA cdrom and 2 WD 1TB black SATA hard drives. Everything runs smoothly and had zero issues with WHS installation. Current drivers are available from Gigabyte website.
I have also used ASUS motherboards in the past for other builds, but not for WHS. Had nothing but good experience with ASUS boards as well.
I am extremely happy with the performance of my server so far. I can stream video to three computers at once while copying a DVD using My Movies disc copier without the hint of a stutter on any of the clients.
Hope this helps!