I have a a64 2800 1.8ghz stock at 2.3ghz stable so far, not bad.

I have 2x 256mb ram @ 333 and a ddr 400 stick of 512mb

You think it'd be better to run uh the ddr 400 only with linux (using winblows now) and have another linux box (the p4 2.4ghz htt i used before i setup this a64) with ddr 333 2x 256mb.

I was thinking the p4 could be my webserver (dev) firewall, etc, not sure though if its a great idea never done this.

Also I don't got a switch or router, so the cable modem I was thinking of using the ethernet and connecting via the a64 system over usb 2.0

Any ideas, thanks. I don't have any cash (thus I'm on a crap computer atm) otherwise I'd just get a router to use but can't

The Linux kernel can be customized quite a bit to meet the needs of your machine. It doesn't so much matter the hardware as it does the use of the machine. For someone without cash, an internet connection and an open-source OS is the way to go. You'd be lucky to get a decent Windows setup without spending a lot of money. If you don't know Linux, though, it will take some time to do things as easily as you do in Windows.
ta0kira