Help for the best upgrade

Hi,

I have a dell precision 620, PIII xeon 1ghz, i840 board with u160 SCSI, 512 mB of 800MHz rambus.

Most of the time the memory isnt fully utiilized. I want to upgrade to have a fastert computer, and I was thinking of getting a matched set of the 1ghz PIII Xeons...

Is this a smart upgrade, if I updatew the kernel and use processor afinities to reduce each processor's load? This ought to speed up the system, right?

Since I have a lot of RAM anbd dont utilize it all fore a database, etc, I dont see the benefit. I do tend to run 5+ programs at a time, some being complex mathematical software, in addition to mp3s, outlook, perhaps word, IE, etc.

What would be my best upgrade for this machine, and what would provide thew best bang for the buck?

BTW, two 1ghz xeons will cost me $100 + plus heatsinks
256 MB Rambus memory will cost about the same...

Many thanks

JMH