Should I pay 500 to mod my old Mac MR-67 tuner?

This depends on what you want. Do you want the 67 to sound better,and thats all you need, go with it. It would cost you $200 probably just to have make align and service it. But to alter it, I don't know.( and I think RM is a tuner God, but it is still altered) It does hurt its resell value and collectability somewhere down the line, though you say your not going to sell. Or do you want to go ahead and spend the $300 or so more on what truly is a better tuner and never lose your investment? Sonics, I would think you would have to go with the 71, even after RM mods it. You might go to groups.yahoo.com/group/FMtuners and pose the same question. Those guys live and die tuners and tuners mods, it would be interesting to read their opinions. But mine is go with the 71. Great problen to have though.

Sounds like you already have your mind made up. If you are happy with your tuner, you should at least consider talking to your area McIntosh dealer; and finding out what it might cost to have your tuner restored to factory specs. You might be pleasantly surprised how much less it would cost. I
suspect it would be way below the $500.00 figure. I have a
newer McIntosh tuner, an MR-73; which my local Mac service dealer restored to "like new" condition. This included replacing the signal strength metering circuit, alignment,
cleaning, and replacement of several bulbs. Not only does everything function perfectly, but the FM stereo is a daily
delight to listen to. The cost was only a little over $200.00 and if I decide to ever sell; I have a perfectly functioning tuner. And do keep in mind that most McIntosh fans do like their equipment in unmodified, but perfectly functioning condition.

The MR 71 engineering corrected several problems that were inherent in the MR 67 and MR 65 designs. A better use of $500.00 might be to put it towards a mint MR 71. They seem to sell around $750-850 range. However, not all MR 71's are created equal. As in every electronic component there are variations in parts quality (depending on the manufacturer of that specific part) that can have a direct effect on sound quality. Generally the MR 71's are very warm and smooth. Sometimes you will find one that is way above the rest............

Don't forget to ask the guy doing the mod what he thinks. He should have more insight to his mod than anyone.