New PC requirements

Hi, I have $1000AU to spend on a new PC box and would like to know good specs for the PC. I need to know motherboard type etc.
The processor needs to be 1500Mhz, P4 or AMD?
The RAM: 256Mb DDR, or is their better?
Geforce video card: the bigger the better.
all other componenets i already have. The main use of the PC will be multimedia mayhem w/ macromedia products and i would like to play some games on it as well.
Thanks