Gaming Machine Components

I'm trying to build a gaming machine, without spending a fortune (around
$1000CDN).

Here are a few things I want advice on:

::::Intel Pentium 4 w/ HT -vs- AMD64::::
I'm shading towards the Pent. 4 because there aren't many AMD board that are
PCI-Express compatible for a good video card...what do you think?

::::Video Card::::
I don't want to spend a fortune on this...probably not more than $300. From
what I've found, this is the best deal / performance / price, but I'm happy
to accept advice. An MSI NX6600GT (128mb PCI-Express). I found it for
about $250CDN.

::::Motherboard::::
I'm completely lost here. Basically, I want to be able to use PCI-Express
video cards (I understand they are significantly better than AGP), good
quality/speed RAM...other than that, I can't think of anything specific.
Nothing has to be onboard as I plan to buy the video and sound cards. If
LAN is onboard, that's fine, or I'll buy a card...not really a factor.
There are just so many out there that are so similar.

::::RAM::::
Well, in the last year or two there have been so many new types of RAM come
out. What would I be looking for to maximize performance, while keeping in
mind that I'm trying to keep costs down. I'm wanting at LEAST 512, but a
gig would be nice.

Any other suggestions you guys/gals have would be greatly appreciated.
Thanks for the help!