This is so subjective, but let me try.
I have a vintage pair of the L-26's, bought from a friend a couple years ago. He bought them from the original owner, who had them re-foamed. In my listening room, the JBL's are the back speaker, while the front speakers are Klipsch KG 3.2's. Both are 2-way speakers, and often (but not always) can be found in similar price ranges on the used market.
They are powered by a modern Denon AVR, so that might not be a good comparison to your Marantz. Mostly I listen to classic rock, alt and some jazz. The system is also part of a 5.1 surround, for the occasional movie. But they're mostly for music, and movies/TV are an after thought.
I have no complaints about the JBL's, and one of the few things I'd consider replacing them with are other JBL's, such as the L-36 or higher. Some say JBL's are geared for rock, but I"m not sure if that's just a cliche or not. Even though they're currently my back speakers, I had them as the fronts for a long time. Just recently picked up the Klipsch, so I'm still experimenting on which I want up front.
One of the nice features on the JBL L-26 and L-36 (and many others) is the ability to adjust the high frequencies. You can dial them up or back, as your preference dictates. The bass response is very good.
To compare them to my Klipsch KG 3.2's, the Klipsch seem to hit 'brighter' highs, an attribute to their horn tweeters. I haven't decided yet on which I like better, as they both handle rock, alt and jazz quite well for my ears and budget.
Hope all this rambling helps.