3 guitars sound awesome if arranged right, ex. lynyrd skynyrd, allman bros. but it does depend on your style of music. judging by your user name, I'm gonna try to take a stab at your style of music (I could be wrong). Is it punk?
If it is, 3 guitars would be somewhat useless. 2 might work but with 3 you've got to worry about who's playing rhythm guitar, who's doin a solo,trading off the solo, or in your case, who CAN solo! BTW to your friend that can't solo, you need to get him on this site, it has alot of lessons on soloing, scales, and stuff like that.