New speakers for an old receiver

That's a beauty, but only 20 watts.

The good news is that if it is in good condition, it will probably sound better than ever with the right pair of modern speakers.

SO look for high efficiency speakers, 90db+, the more the better, that will enable the most out of those 20 watts. Klipsch, Tekton, Zu, JBL, Triangle, some REf3A, Audiokinesis are a few that come to mind.

I'd love to hear my Triangle Titus XS speakers on that. Triangle has a very fast and clean sound, a nice match to the slightly warmer sound I recall from that old Marantz. Triangle Titus can be had used for under $500, not a bad and inexpensive place to start.

BA A 26 monitors ***** whathifi review UK

I own a couple of vintage receivers/amps and have good luck with both Paradigm and B&W monitors. The paradigms are easier to drive so that would be my first choice.

With the less efficient small speakers/monitors, expect some extended bass response at low to moderate listening volume, but also to run out of gas quickly if/when the volume goes up.

Worth considering if you prefer to go louder and clearer and give up some bass extension (higher efficiency smaller speakers in general) or go for more bass at low to moderate volume (lower efficiency smaller speakers in general).

The other way to go is with larger high efficiency speakers that may or may not also cost more depending. These will in general give you more volume and low bass extension together. Zu and Larger Klipsch models might be good and more affordable options for that. But in general quality speakers that bigger and more efficient and have good bass extension and good sound quality top to bottom will be quite large and cost more. Plus, many of these are really designed to perform best with lower powered tube amps, though a decent SS device like the Marantz would of course still work.

Sorry if too much info maybe. Of course any speaker will work. But if you are looking to max out performance in a certain way, I think this is useful stuff to consider. A 20 watt amp can go a long way in most any case, especially in a smaller room. Its just a matter of how far you want to go and in which direction. That's what makes this stuff interesting (maybe).

get JBL 4812. Not modern, but simply BEST for your setup.