Hardware

This is my my first m0n0wall build, and I'm in the planning stages right now.
This box would be serving as a firewall for my friends and I. They're heavy into P2P/Usenet, and I don't want to sacrifice too much speed for the sake of a more secure network. Right now it's five of us using a 5mb cable connection.

I want the m0n0wall  box to be Pentium III based, which would probably be overkill but its cheap to find the parts on ebay, and also its great performance with very little power usage.
I would also like to have a gigabit network, so it would probably be best to purchase a gigabit switch.
But if i were to use two PCI network cards for the m0n0wall box, wouldn't the ethernet throughput be limited by the PCI bus? I had looked into PCI-Express network cards, but they're pricey.

Any help/advice would be much appreciated, thanks 

PCI-X nics?  Your no longer looking into a P3 solution then.  Your throughput would be bottlenecked by the PCI bus, butreally IMO your best bet if your wanting performance would be to obtain a decommissioned Firebox, or a newer WRAP to use as your platform versus a pc. 

Thanks for your response.

I had looked into the WRAP and Soekris boxes before I decided to go with the Pentium III, but I'm sure that my throughput would be even slower.

Taken from the m0n0wall facts page:

On a net4501, m0n0wall provides a WAN <-> LAN TCP throughput of about 17 Mbps, including NAT, when run with the default configuration. On faster platforms (like net4801 or WRAP), throughput in excess of 50 Mbps is possible (and > 100 Mbps with newer standard PCs).

These pages also seem to confirm it:
     http://www.smallnetbuilder.com/content/view/24696/85/1/2/
     http://www.smallnetbuilder.com/content/view/24689/51/1/6/

Any other options?

EDIT: what about a product like this: http://www.intel.com/network/connectivity/products/pro1000mt_dual_server_adapter.htm

Ok here's how I made my decision:  The 4501 was free.  hehe, ok now seriously I'm all about speed like you, but with the 4501 and it's 15mbps limitation.. it is not the bottleneck on my network since I only have a 4mb connection.

Now I do not know how to convert a 33mhz pci bus into a measurable throughput in terms comparible to a broadband connection.  They could be very similar, or distinctly different.

I choose to stay with the 4501 because of it's footprint.. it's no bigger than the PIX 501 on my desk now.  Plus little to no heat generated as well as barely any electriciaty and no moving parts.

But your mileage may vary..  if your very interested and both time and parts are a'plenty I would setup a p3 box and test it's performance.

I did some research, and the PCI bus has a max throughput of ~133 MBs, and with my 5mb cable connection, I should be fine.

Thanks for your input 

Seriously...  you're talking about *5* Mb!    Yeah, like you said, you don't have to worry about the PCI bus. Nor do you have to worry about the processor, or NIC's, or anything else. Anything you can use will push more than 5 Mb. A PIII is more than adequate, a 486 would do fine for 5 Mb.