With three Gtrs you could certainly get more sound, it could be very messy.
I have seen local bands with three gtr players and professional players certainly have three gtr players:
www.longislandmusicscene.com/phantomplanet_performance.htm
It's not past doing three gtrs on their own
you could almost do without a bass player (though I think bass is very important) It could be a White Stripes set up where one gtr plays a drum rhythm another could play the bass part and so on...It could be very inventive.