I had a certified technician who I've known and trusted for a long time put IEC's into my Conrad Johnson Premier 12 mono blocs. Best move I've ever made. While they sounded perfectly great with their captive stock cables (and a noticeable step-up they were when compared to much of the other "captives" out there), playing with the aftermarket cords has dramatically improved the quality of my system and the ability to customize the sound is truly condiment(s) to the smorgasbord. Priceless. Well worth it. Don't hesitate, just do it.
BTW, if it's the ONLY modification done to an otherwise stock amp, I agree it will probably INCREASE its marketability and value....The one thing that discourages me from otherwise being attracted to vintage gear is knowing I have to get the IEC's done. Generally speaking, why be stuck with stock captive power cables when there is so much more potential within virtually all amps when you partner them up with a cable that enhances/synergizes "Just right" for your own system!!! Enjoy.
BTW, if it's the ONLY modification done to an otherwise stock amp, I agree it will probably INCREASE its marketability and value....The one thing that discourages me from otherwise being attracted to vintage gear is knowing I have to get the IEC's done. Generally speaking, why be stuck with stock captive power cables when there is so much more potential within virtually all amps when you partner them up with a cable that enhances/synergizes "Just right" for your own system!!! Enjoy.