I'm having the damndest time trying to find a LAME encoder for mac, and the one i'm using for iTunes right now I can't figure out for the life of me. I guess it's like an addon to iTunes, but, as said, I can't figure it out.
xACT is not what youre looking for then, and I dont know what you are looking for. You may want to try the boards on the apple website, those folk know everything there is to know about their computers.