I thought ABCNavigator was a front end for abcm2ps!
(I installed it but never really go into it, prefer to do all my abc stuff on the Linux command line)

abc2abc is part of James Allwright's abcMIDI package. It does do transposition. It also has a rather odd command line syntax, and it's fussy about what it calls errors but aren't really (like starting or ending with an incomplete bar)- fortunately it has a switch to make it ignore such complaints. It's stuill very useful and as well as transposing the notes it converts chord annotations too.

Anahata