Need Motherboard Advice

Greetings, I am planning on purchasing a new PC and I've got a few
questions.

It'll be a P4 processor, most likely the 3.0 GHz model. Along with it
I will have 512 MB DDR at 400 MHz, an 80 GB HD, a 17 GB HD (from old
machine), 40x16x4 CD-RW (from old machine), and a Radeon 128MB 9600.

The machine will be running Half-Life and Command & Conquer Generals
to start, but I'm hoping to get Half-Life 2, and some of the newer
games out there my PC can't handle.

1. My problem is that I have no idea what motherboard I would need for
this job, but I'm assuming what ever one I get the onboard audio codec
and the network card will be better than my old SB Live! Value and
3COM from 1997. The only boards available at the store I'm going to is
ASUS so that's what I'm getting... I just don't know which model is
best.

2. I need a reccomendation for a good set of headphones that I could
use that have a mic on them. (I'm tired of speakers)

3. I'm not sure if the Radeon 128MB 9600 PRO or the Radeon 128MB 9800
PRO would be better investments than the 9600 standard edition.