To make my ringtones, I use Wavepad.
There are a ton of different ones you can use though.. google is great lol.

Every program is a little different as far as amplifying volume goes. Some don't have an option for it at all.. just a matter of finding a program lol

If I remember right, there are some ringtones also somewhere around these forums that are loud. I can't remember where or a link right now.. but try searching and see if you like any of them?
(or someone else come post a link.. haha!)