Dynaco made a name for itself in being the most inexpensive components sold which could be tweaked for a few dollars to mimic high end components costing 5 and 10 times more.
Actually Dynaco made some very solid vacuum tube gear back in the '50s and '60s, just like Marantz. And just like Saul Marantz, David Hafler was the engineer who made the company, and whose absence left the brand considerably less valuable.
OTOH Dynaco was among the first to produce a high power (>100W/ch.) transistor power amp in the early '70s, the Stereo 400, rated at 200W/ch. (Note that doubling power produces a barely noticeable 3dB increase in loudness.) The Stereo 400 was often modded (as were many high power transistor amps of the day that weren't as stable as the Crown DC-300A), and also available via Heathkit as a "Dynakit" build-it-yourself kit. That was a separate era from the Dynaco tube years though.

Don't forget all those caps that are likely to be dried out. One thing that any keeper of vintage electronics should be in the habit of doing is replacing at least the electrolytic capacitors and other components that degrade over time and/or with use. My c. '70s H-K Citation 19 is going to the shop RSN to get an overhaul again, so it will keep running well for another 10-20 years.

70s gear is liable to have noisy pots and intermittent switches, unless it was really good quality or has been expertly serviced.

Thanks but I gave up on buying the Marantz a long time ago.
"All persons living and dead are purely coincidental" Kurt Vonnegut

I would suggest a McIntosh or an older tube type receiver. Fisher and Marantz are good choices. Dynaco made a name for itself in being the most inexpensive components sold which could be tweaked for a few dollars to mimic high end components costing 5 and 10 times more.

No doubt about it.
If the truth were to be made known, laughter would abound - Chinese proverb

Love the song "Nature Boy"; the song's message is true.
Am I not destroying my enemies when I make friends of them.

Happy listening!

Thanks for your comments. They have been very helpful.
The greatest thing you'll ever learn is just to love and be loved in return

• Nature Boy

Rotel has had a solid reputation as a good mid-range hi-fi manufacturer.
Good call on rewiring the sub. IME proper loudspeaker hookup and placement makes a larger difference in the sound than buying new electronics. Cheers!

Thanks for the suggestion. I know Harmon-Kardon was good because I used to own one. I've decided, however, to stay with my Rotel. I had some technician rewire the sub-woofer so it sounds much better (it was out of phase).
The greatest thing youll ever learn is just to love and be loved in return

• Nature Boy

First of all, circa 1970s isn't quite vintage for Marantz. By that time the brand was only fair. The really hip and cool collectible stuff was made before the company was purchased by Superscope in 1964, and still made in the US. You'll have to pay top dollar for one of those old relics, and you'll be disappointed by sound quality that's only so-so by today's standards.
If you want a good integrated amp from the '70s, I recommend the Harman-Kardon A402. The engineering was solid, sound quality was superb, and the LED display still looks cool. Needless to say, you'll need to replace each and every capacitor to get the original sound quality. While transistors seldom fail, caps do dry out eventually. My Citation 19 (with the same LED display as the 402) is going in for an overhaul for just that reason!