On another forum people have said that WAV files naturally play louder than mp3 files. When you increase the volume of a WAV file it will sound a lot louder than the exact same amplified mp3 file.
So I decided to do a test. I got a ringer of a old fashioned bell ringer in a mp3 and a WAV format. I increased the volume of both of them to about 250%. The mp3 file is louder than the stock ringers on the 8830, but still low especially if you are out and about.
The WAV ringer file is so loud you can see heads turn even in a crowded subway or noisy street. The only problem with the WAV file its quite large, about 715kb. However you can put it in a memory card so it won't take up system memory. I don't have a card yet so I just put it in the phones main memory.
I have put the WAV ring file at the following location, so just cut and paste the below link to download it.
http://members.aol.com/hrdc/WAV_OLD.wav