WOULD IT BE DUMB TO BUY A MARK LEVINSON NO 23.5

I'll second comments that its a bit sterile sounding, but i'll also second comments that its well made.  And while electrolytic capacitors degrade with age - my experience, having shipped -- and seen the results -- 100s of units is that if you really use top quality parts, and run them well within limits, the problems begin 30 years out - not 15.  Yea, i had some cap failures but in retrospect the problem was usually a modest oversight on my part. Ive frankly had more problems with new Chinese capacitors than with old US and European made ones. Or the quality Japanese brands.  Caveat emptor w/r/t specs.

Now, on to re-capping without schematics.  remove cap. Look at specs.  replace cap.  Who needs a schematic?  yes, they are nice to have to identify critical components - but we're talking preventative replacement of things that go boom - not subtle circuit tweeks.
I'll leave the sonic value judgement to the only one who matters.  You.

@itsjustme, search the forum and web regarding recapping and servicing legacy Levinson amplifiers. It’s not as simple as a part swap, the labour to get at the components is outrageous.  In addition, Levinson masks parts values etc. A lot of very capable service techs refuse to work on Levinson products. Unfortunately, I know this first hand. 

If you have Maggie's, the 23.5 was the cat's meow at the time. I remember it as having cavernous power reserves and rather liquid, but imagine it would be like owning an old Jaguar--good memories, but now a money pit and the company has moved on.

Send it to Pyramid audio in Austin, Texas.   They are a Levinson authorized service center.   I had them service my ML 33h.

Enjoy and good luck, 
Jose

The thing with vintage Levinson amps you should be aware of is not the power supply capacitors but the EMI suppression caps (Rifa PME271) across the mains voltage. These apparently do not age well and fail short, creating a fire hazard. I had one of these fail on my Levinson 20.6 -- saw a wisp of smoke and shut it down, and still there was burn damage on the pcb. Then I replaced all those caps in both amps.

(Here is a picture of a 23.5 for sale as is for parts:
https://www.usaudiomart.com/details/649367673-mark-levinson-235-for-parts-or-possible-repair/images/1595023/
the fire started at the front of the amp where the power supply board is located).

When I got my 23.5, the first thing i did was to replace all of the EMI caps. It was a bear of a job because both heat sinks had to be removed to get to the front board and then there was the spaghetti nest of wiring to contend with. The power supply caps were easy to replace since they are held in place by cap brackets and the wires are connected by screw terminal to eyelet lugs. You can move the heat sinks out of the way without desoldering any wires since there is JUST enough play in the wires for the caps to clear.

Worth it? IMO you would have to spend upwards of $20k to get the same kind of low end unlimited current delivery performance.