The Mod is Firefox PreLoader, which puts the Ffox .exe into startups. It does make Ff load much faster but means that it is in memory all the time, unless you unload it, in which case it takes an age to reload if you need it again.
K-Meleon is good, I am using it a my default browser, the only downsides are:
1. There is no sidebar, so you have to use the menu or tool bar for Favorites and history. (One is promised for the future)
2. A lot of the configuration is done by editing text files, although this is fine tuning stuff that you may well not need.
It can use either IE Favorites or Mozilla Bookmarks by enabling/disabling the appropriate plugins in Edit~Preferences~Plugins.
I use the Favorites option as I then have only one set to worry about.
I think that Firefox has lost the plot, it was supposed to be small and fast, but is now bloated and slow. Have you looked at Flock? This is based on Firefox but claims to be faster. Only runs on W2K or XP.