Yahoo Messenger and notification sound

[mshelf3]

I am going crazy with trying to find either a messenger program that will not disconnect me for no reason (like meebo) but will let me change the sound or ringtone for incoming messages and that will allow me to receive Yahoo Msgr. I can't change the sound notification for Yahoo on my EVO. Does anyone either know how to do that or can recommend an app that will allow me to do all of the above?????