Even if this were possible, the phone can only deliver so much power to a speaker and I'm guessing it's already close to that limit at full volume. Trying to go louder could risk distortion and possible speaker damage.I'm pretty sure the volume is controlled in the system and the only way to change that would be with root, if it can be done at all. I don't think a 3rd party app can hook into that to make the change.
Yep but to some it's worth the risk. Over on XDA someone made a mod to use the ear piece as a second speaker to create stereo mode. I stopped following the thread but I'm pretty sure some people blew the ear piece because it's not designed to be used at the same volume as the speaker.Even if this were possible, the phone can only deliver so much power to a speaker and I'm guessing it's already close to that limit at full volume. Trying to go louder could risk distortion and possible speaker damage.