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. 

The MC240 is an awesome amp.  I love 6L6s and am thinking my first build is going to be a 6L6 amp as I am trying to learn more about amp design.  I use a pair of 845 mono-blocks that are 45w and usually speakers that pair well with 845s also do well with 6L6s.

I say that to say this.  I make monitors that I think will work well with your amp.  Depending on your taste, I have two that are pretty awesome.  One is rather soulful and very musical (Nightshade) while the other is more true and refined (Blackthorn) and are under your budget.  Both offer superior detail and a huge soundstage.  I think you would be pleasantly surprised if you heard them.  If you can, come see me at Captial Audiofest room 525.  Otherwise, we offer a 30 day in-home demo.  

Other speakers you have to demo if you can:

Check out the Raidho X-1s.  They require some space (9' between the speakers, 3' from the wall) but deliver an amazing soundstage.  They don't have the best bass response but are good sounding speakers.

Obviously the Magico A1, the B&W 805 D3, Monitor Audio Platinum 100 and Legacy has a monitor you should try and here.  Paradigm has a monitor you should hear and Sonus Faber.  

If you hear all of those you will get a good flavor for what you are looking for and you are bound to like one of them a lot.  You have a great space for a monitor speaker as long as you can get that 3' away from the back wall.  

I'm currently leaning towards a pair of Aerial Acoustics 5T.
Any thoughts?