I might have missed it, but why can't you just slap on a gigantic cassette on the back instead? Instead of changing my chainrings, I upgraded to an 11/32 cassette with the commensurately larger capacity derailleur to handle the extra chain needed. Made a HUGE difference in going up hills, and I didn't have to fuss with the front part of the drivetrain, which seems to be more of a hassle to "upgrade".