"Original" equipment vs. upgraded equipment

For me, I would not discount an upgraded unit from the manufacturer.
Sure, it may have some older parts, but I trust the manufacturer to know what needs replacing and what doesn't. If some people are so anal, then let them pay the premium price.
This is why I buy from Ayre, Atma-Sphere and McCormack. 
I never have to worry that my equipment will be obsolete. Far better than buying another new unit and eating the depreciation.
Bob

One example would be an ARC Ref 75 being upgraded to a 75SE. Is the upgraded version inferior to an original 75SE?

In this example I would say that though the upgraded unit may sound the same, the original 75SE will have greater resale value on the used market.

Why? Because in the upgrade process, only certain parts are being upgraded, not the whole amp. So if you are buying an upgraded used 75SE, 70% of your parts may be a couple/few years older than a used original 75SE.

Outside of that, there are qualified modifiers outside of original manufacturers. Folks like Steve McCormack, Chris Johnson, Bob Backert, Bill Thalmann, and others who perform modifications outside of the original manufacturer. Many of these certified modifiers products may idea sound better than the original. However, you will lose about 80 of your modification investment on resale.

Then there are other lesser qualified modifiers (all DIYers), whose work actually devalues the original product on the used market.

I don't want to sound like a crabby old fart, but precision in language counts!  Upgraded vs. original is not the same as modified vs. original when you are describing a unit for resale or determining what you think its value is.  At least to me, an upgrade is a change in the internals of a unit developed by (and in many cases done by) the manufacturer.  Like the Vandersteen 3 to 3A to 3A Sig or a VAC Ren 30/30 to a 30/30 Sig.  In my mind, the value of such units is increased as they are brought to more current designs and parts.  The value of modified units may or may not be better, based on who did them, how well they did them, etc.  While you won't get your investment back at resale, a unit modified by Dan Wright or SMc Audio will be more valuable than a stock unit.  OTOH, we've all heard (pun intended) of backyard butchers who return units in less than fully functional condition, if they return them at all. 

At least to me, an upgrade is a change in the internals of a unit developed by (and in many cases done by) the manufacturer. Like the Vandersteen 3 to 3A to 3A Sig or a VAC Ren 30/30 to a 30/30 Sig. In my mind, the value of such units is increased as they are brought to more current designs and parts.

Yes, the value is increased, no doubt, but not up to the level of an original Vandersteen 3A Sig or VAC Rev 30/30 Sig in your stated case.


Look at what @oregonpapa  did:

I owned the REF-75. Replaced the KT-120’s with the KT-150 for a nice upgrade. When ARC came out with the REF-75-SE I sold the REF-75 and bought a new REF-75-SE. 

There is a reason for this, and I just did something similar.
I just bought an original ARC Ref 5SE, and now have my ARC Ref 5 up for sale.
It would have cost me another $2,000 to have ARC perform the upgrade to 5SE, and even then, they are only upgrading some of the internal parts (maybe 20%).
When I am buying used items, I always get the serial number to look at the age and service history of a component.
Eg: I would rather buy a 3 year old original component than a 7 year old component that was upgraded 3 years ago, as would most others. 
The 3 year old original will have more value on the used market than the 7 year old upgraded version.

Bottom line: Updating a few of the parts doesn't make it equal to a newer unit. Hence the value of an original unit is greater on the used market than even a unit upgraded to current standard.

The value of an upgrade has a great deal to do with who is upgrading it and the degree to which it is being upgraded.  The upgrades I mentioned in my previous post involved new circuit boards, replacing the originals with upgraded capacitors, resistors etc.  You need to discuss the upgrade with the upgrader and get to specifics of what improvements they can offer at what price point to evaluate the overall value to you, the owner, of that upgrade.