I'm not sure that I would recommend a complete rebuild, in large part due to the cost involved. The capacitors are the least reliable component (after the lamps). The semiconductors are generally very reliable.
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Marantz cheaped out, at least on their lower end models in that they used quasi complimentary output stages. In contrast complementary symmetry output stages are more linear but require matched NPN and PNP output transistors. The PNP devices were more expensive so manufactures opted for the quasi symmetry output stage instead, using only NPN transistors.
... I also have a Sansui QR-3500 it sounds better than the Marantz. It has a complementary symmetry output stage. Both units still function with (mostly) original capacitors. As time permits I may recap both those units.
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I dunno... at the current resale prices, if you entry level is free (I paid like $50 bucks in '86 for my 4215 and the 2325 was free) spending a thousand bucks on the rebuild is worthwhile.
Obviously, I would not recommend doing this on a 2220B or 2420... perhaps a 2275.
The quads, that's an interesting issue. I'm attached to my 4215, and I have the SQA1, RC-4 and original walnut case, and I like the way it sounds in a secondary system in my office, quad, so I figured WTH and went with it. The thing about the quads is that they are much more complex so the cost is pretty high, so you really have to think about it.
The problem with only doing the caps is that these things are old by now and there's a lot of other parts. Relays for one... and those small semiconductors -and relays- go. And the traces on the PC boards. It's a lot of stuff that goes and once you've dug into the receiver, taking boards out and what not, you might as well spend just a little bit more money to redo the entire board.
Caps... modern caps are definitely a worthwhile investment. My 2325's power supply sports 25% more capacitance -and faster caps- than OEM.
However, at some point you need to stop and figure out if you want it pure vintage or an upgrade (hint: I don't recommend that). My Sansui G7500 had cooked its TO3 high speed transistors... I had the chance to go with a more reliable lower speed version but I chose to keep the original. They are not as reliable but their sound is awesome.
Indeed, the G7500 comes from the time when THD and IM distortion were both rated at 0.025%.... The Japanese had gone into DC coupling and high rise (slew) times. The result is that in four years, from '74 to '78, the sound had cleared up incredibly. My Sansui sounds far more modern than the 2325. Absolutely so.
So, my recommendation is simple... the labor to replace all those caps includes taking out all the boards and strip the whole receiver. If so, why not just spend an extra 20% and redo the whole thing.
Oh, two more things... I don't care for LED lighting and the capacitors types are also consistent with their location in the receiver. Don't assume that you can replace ALL caps with the same type.
That's why I had mine done by a guy who's being doing this for years.
