ARC LS15: did they ever use Mundorf MCaps on it ?

If you are truly interested in buying this preamp your best solution is to have the seller send it to Audio Research to be checked out. Once Audio Research has given it their approval they can forward the preamp to you after you have paid the seller. I have done this several times with great success. It relieves the seller of liability and the buyer knows he is getting a unit that is working properly.

"the key words are "as long as it's done right"."

It was done right when it left the Audio Reseasrch factory. Have you ever seen the facility at Audio Research? If you did you would never trust some guy in his garage or little shop with no real knowledge and no equipment to speak of other than a soldering gun. As far as I am concerned these guys are shysters just looking for a way to make a buck by leading you to believe they are going to enhance the sound of your already excellent sounding equipment.