Monitors for a 240

I have an extensively rebuilt and modified 1961 MC240 which in stock form sounds lovely. Most 240 in decent shape make 48-52 wpc at reasonable distortion levels. The amp is capable of driving many speakers. Your choices w moderate volumes are near endless. You might find the footprint of a small floor stander equal to a monitor w appropriately sized stands.  Monitors I have enjoyed of late include TAD, ATC, Sonus Faber and Vandersteen VLR-Signature
Enjoy your journey!

For your size listening room and the type of music you like, I don’t think you will go wrong with the Harbeth P3ESR. They are my favorite small monitor type speaker. BTW, I have owned many speakers and I always go back to the P3!
https://www.stereophile.com/content/harbeth-p3esr-40th-anniversary-edition-loudspeaker

I agree with yogiboy. I haven't had the pleasure of hearing the P3's,however I recently acquired a pair of Graham Chartwell LS 3/5's,and before those,I had a pair of Spendor S3/5's. There is some serious magic in those British mini monitors.