Install IEC male socket or not??

If I had that amp I would want to do it, but I would contact Jon Soderberg first to get his thoughts. It won't hurt to try if you already haven't - or, contact Pass, they might do this for you. As long as Jon or Pass provides the upgrade, I don't think you should worry about a diminishing resale value... JMO.

I've installed IEC connectors in multiple vintage amps, and some of them I've sold with no concern from sellers or apparent impact to value (ie anything it was a benefit). I was completely open about the fact I added them and that I did it myself. Frankly my first one had some issues of workmanship (a gap) and the buyer was perfectly happy with it.

If you are of a mind to do it yourself, just be aware it's very hard without a die/punch to get the hole cut out perfectly. A dremel tool really doesn't work on heavy gauge steel. I end up using a combination of drill bits, nibbler, hand file, and dremel grinder. It's tedious.

I really wish I could find a punch for the exact hole size, but I haven't found one yet.

Also, check inside your amp. Some of them are a real bear to properly place the receptacle without interfering with other components. An alternative is to install one of the cord end IEC connectors on a pig tail, but I thing those look silly and am not sure what they accomplish over simply installing a good quality captive cord.

Bdgregory states it correctly. I have done IEC's in a number of components, very worthwhile from a sonic standpoint.

I agree with the above posts in that you'll appreciate an iec for a better aftermarket power cord. Those 200 watts will appreciate a larger guage cord and your ears will appreciate the improved sound as well.