Help with McIntosh Repair Facility

My MC452 is having an issue with the right channel that's a little weaker than the left.  Not by much but definitely noticeable.  Have been trying to diagnose the issue and everything so far points to the amp. I'm using XLR and have changed ICs , preamp tubes, cleaned amp inputs, etc.. but the head scratcher is if I switch the right and left IC inputs on the amp the sound or output is balanced. The meters are in alignment as they should be. The only issue is of course the right and left channels are opposite now.   I've spoken with an authorized repair center and bench testing is $350 and worse case scenario the board needs replacing plus labor can hit $2500 which in my opinion is ridiculous.  Has anyone experienced this issue or have any ideas or know of a reputable or more cost effective repair facility? I'm in Lexington KY.  Thanks in advance.