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

OP says M-caps not M Supreme if I recall correctly.
As we can see there are several members here who belong to the school of die hard "keep it stock". I respect that but I personally am a "respect the mods as long as its done right (get close up pics), as long as you research the sonic character as the components replaced."

Johnsonwu,
the key words are "as long as it's done right".
I cannot check in any way if it's done right at some thounsands km from the seller; and if the seller says he did not modifiy anything and I just 'caught' him, he may lie on many other things, maybe not so easy to see...

Moreover, I'd like to know how the original ARC design sounds; then I may even want to improve or change something in time, but firse I need to know the starting point.

Last, I don't have the chance of listening to the LS15 (neither stock nor modded) before buying, so I may not like it: I don't know how it works in USA, but in that case in Italy it would be very, very, very difficult to resell a modded object. I should almost give it away for free (well, ok, it's an hyperbole, but I guess you got it).

That's why I'm looking for an original preamp. :)

Close up photos will reveal workmanship of the mods.
If lack of reference point (you dont have friends who have a stock/similar unit) and resale value is an issue where you are then stick with a verifiably stock unit.
The LS15 is not that expensive. By the time you send it to Audio Research for check and retube and stuff you might as well pay a premium and buy a stock unit.

To my knowledge Audio Research never used Mundorf caps in production. They used Rel,Infini and MIT in older units. Hope that helps.

I would always choose a Mundorf Cap'd unit compared to a stock one.