Emergenc ybrake problem

Had my nissan maxima worked on. Resonator and pipe repl. With rear brake job. Before going in emer.
brake handle would come up 1/2 the way and hold the car. Now it goes as far as travel is permitted and
still does not hold. Am told by mech. The rear calipers
need to be repl. To remedy. There is too much travel
going on in the handle to warrent this I think.
There is about two inches more of cable coming up
and don't think there is that much travel involved
in the cylinder slipping, as the mech claims, to cause this. I hear when under the car and someone operates the brake handle, popping just above the
heat shield above the resonator and he says this popping occurs back at the calipers. Don't think he
is diagnosing it right. They want around 600 bucks
more to do this. What do you think?
Thanks, Joe in Ill.