Have you thought about bypassing the mouse altogether for scrolling?
I use the page-up/page-down keys and its much easier. I fly though web pages.
Even better, I have (with the help of someone from the Firefox forums), re-mapped these two keys from their original position on the right-hand side of the keyboard (which I find awkward), over to the left of the keyboard, and to two keys I rarely if ever use;
The CAPS-LOCK key (which is now Page-Down), and underneath it, the Shift key (now Page-Up).
To try this out, you will need to edit you're .bashrc file (in your home directory), and add these lines:
xmodmap -e "keycode 50 = Prior"
xmodmap -e "remove shift = Prior"
You will also need to add the following to .xmodmap (if you have one, or create it in your home directory):
keycode 66 = Next
(If the keycodes are different for your CAPS-LOCK and Left-Shift keys, you can use the 'xev' program to find them out.)
Now, I should say that editing these two files is the only way I've been able to get the functionality I wanted. Its quite possible that someone more knowledgable than myself will come along and do the same by editing just one of these files, but untill then, try this, you may never use your mouse scroll wheel again