The BOLDER Cable Company has never modded the SA-XR55 or 57 receiver.
We modded the SA-XR25, 45, 50 and 70 receivers.
Panasonic started changing the receivers too quickly for us to keep up. The back panel has changed quite a bit with each model and required a different binding post mounting plate for each model. We had to have a new plate designed and produced in a decent quantity to make it worth the machinists time.
Panasonic keeps changing the design so the plates we have had made are not useful any longer.
I do have a stock SA-XR55, but I have ne'er even opened it up. I am not sure what is involved with mods.
I might be interested in a one off mod of such a unit, but the cost would be between $1200.00 and $1500.00 and take at least a month.