I'm working on building an Internet Gateway box for a SOHO application, consisting of the following:

-Firewall/NAT/NIDS
-Web/mail proxy
-VPN
-Router/wireless access point

I'm still working out the details of all the packages (squid, freeswan, spamassassin, etc.), but I wanted to get some input as far as hardware goes. The network consists of a varying number of client boxes running Windows, both wired and wireless, as well as a web server (Apache, FTP, mail server with webmail and mailing list) and a file server (samba).

It needs to be small and easily maintainable. Here's my parts list so far:

-VIA EPIA PD 6000E (mini-itx motherboard with dual LAN)
-512mb PC2100 ram
-40gb 7200rpm Seagate hard drive
-Linksys PCI 802.11g wireless card
-Travla C158 90w mini-itx case
-Slimline CD-ROM drive

So, I three hardware-related questions:

1. The board was picked because it is both fanless and has dual lan. However, it has a 600mhz Via processor, which is probably equivalent to a 450mhz Pentium. I'm wondering if it's powerful enough to handle both the software and users. There will be under 50 users on the network, with a maximum of probably 10 users at a time access the Internet and not more than 2 or 3 VPN users at a time. I'll be using a stripped-down Debian installation. I know it's possible to run VPN and routing functions on things like ~200mhz Soekris boards successfully, so I figure this should be plenty for my application. Yay or nay?

2. Based on those requirements, is 512mb ram too much or too little? If I can get away with 256mb, I'll do it, but I'd rather get more than less. The board only has one ram slot, and getting a gig is much more pricey than 512. So, 512mb seems like a good number for both now and future expansion. Does that sound right?

3. I don't have experience setting up a Linux PC as a wireless router. I picked the Linksys because I know I can at least get away with running it using ndiswrapper. I might have to get a PCMCIA card instead and use a PCI adapter to make it work, however. Anyone have experience in this arena and care to recommend a card and/or setup?

Thoughts?