100 MHz or 200 MHz laptop as a Linux router?

[soloking]

I have a few old systems that I think would make nice routers. Unfortunately, the specs aren't very impressive. I'm basically looking for a dial-up router, with the following features:
Required

• Firewall (iptables?)
• Multiple computers connected to dialup (IP Masquerade?)
• Interface to turn the connection on and off (like via SSH)

Desired

• Automatically turn connection off after inactive for a while.
• Web or GUI interface to manage this connection. I was thinking lighttpd with PHP -- any suggestions?
• Proxy-caching server (like Squid) for a little more speed

Here are the systems:
Digital HiNote VP laptop

• 100 MHz Intel Pentium processor
• 24 MB RAM
• .7 GB hard drive

Compaq Armada laptop

• 200 MHz Intel Pentium processor
• More than 24 MB RAM
• 6 GB hard drive

Compaq Presario desktop tower

• 600 MHz Intel Pentium III processor
• 128-192 MB RAM
• 9 GB hard drive

Dell OptiPlex desktop tower

• 800 MHz Intel Pentium III processor
• 128 MB RAM
• 6 GB hard drive (I think)

The modem is a 3Com Courier external modem, which worked very well with my (deceased) Fedora Core II server. I also have a PCMCIA network card for each laptop.

What Linux distribution and software would be best for each? Damn Small Linux, maybe? I'm fine with something that's all command-line, no GUI whatsoever. I would prefer to use the laptops, because they save space. If I go with one of the towers, I would like a GUI like GNOME or KDE.

[GNU-Fan]

Use Debian Stable.