Xeon, P4 or Athlon MP

Hi,

sorry if we had this already.

Supposed I wanted to setup a real big postgresql-server for some heavy big
webpage running under linux, what would be the best choice regarding
price/performance?

(Basic system with raid and 10k-scsi drives presumed)

quadro Xeon 700 Mhz (1024 kb cache), 4 GB ECC Ram

or

dual Athlon MP fastest possible (1800+), 2-4 GB DDR-Ram

or

single P4 2.53+, 2-4 GB Rambus / DDR-Ram

Does postgresql scale well enough to use the quadro xeon to its capacity?
What exactly does the 1024 kb L2-cache do for postgresql? What about the 2/4
GB mem issue with Linux?

Is this xeon system in your opinion worth the (great) additional costs?
Should I take 2 dual athlon systems and play a bit with rserv, usogres,
eRserver? (how much is this eRserver anyway?)

What are your experiences with high-end x86-systems and postgresql under
Linux/Fbsd ?

Thanks for your thoughts.

Greetings,
Bjoern