Building PC

[Sailor]

A friend of mine asked me to suggest her a nice system. In the beginning I thought "piece of cake" but I realized that hardware keeps changing all the time and compatibility can be a headache. As usual I turn to MG .
Money is not an issue for her but I don't want people to think I am a dumb money waster. Let's say about 1500$.
I think she usually has lots of things running on the same time and does a LOT of downloading. That's why I chose dual-core and much RAM. Should I go for Intel or AMD dual? Here are some CPUs I have in mind
Intel
AMD

I have concluded to the VGA, Ram, Audio card but I need second (third, fourth...) opinions.
VGA:Asus GeForce 7600GT 256 Mb.
RAM: OCZ Performance 2 GB Kit
Audio: Creative Soundblaster 4


I need you to enlighten me on the mo/bo as well. Wich mo/bo can fit the above? Sockets, pins, slots... I'm gonna kill myself.
Thank you in advance.