Don't know what is the fastest browser, but Firebird is very fast, have not tried K-meleon in a while. Just built a win2k system and stuffed Firebird on it. and it works extremely well. but when the system is a 3Ghz CPU, anything loads fast.
I dont care much for Galeon these days, used to like it, they have made changes which arent UNIX like, such as removing the ability to CTRL+U on the URL, and a few other features have been either removed or forgotten. So I end up using Konqueror alot more than used to, and Galeon alot less. I do like Galeon, but its losing its features I liked about it.
The fastest Linux browser would be Lynx & Links, one of the fastest graphical web browsers would be Dillo, http://www.dillo.org/. thats one I had forgotten about. Used to use it alot in the past. but mostly run *BSD without X, so I make use lynx alot.
Dillo is very small too, around 300kb.
Any linux distro will run fine on an older system, if you install it without X, would rather use NetBSD without X on older systems, as it runs on many more platforms than any other OS out there.
I usually run FD Linux, http://www.fdlinux.com/ on older platforms, as it is floppy distro, I've run it on an older 92Mhz Overdrive 486 system with 20 megs RAM, no HD.
found this graphical web browser,
- i jini very small web browser! 66kb! supports tabbed browsing also.
http://www.ijini.batcave.net/- Avant Browser claims on web site to the be the fastest. an upgrade to Internet Explorer. Avant Browser is a fast, stable, user-friendly, versatile multi-window browser.
http://www.avantbrowser.com/