Bookshelf speaker pairing with subwoofer

I just picked up the excellent Studio Electric M4  Monitors.     I'm using them with a REL and I think the fact that they also are sealed acoustic suspension allow them to integrate so well.   

Around $3200 and worth every penny.   

Just a thought to post for consideration....
I've an older pair of Polk bookshelf with no port, but a 6" passive cone beneath it's 6" woof with a 1" dome above all....

Not the same as port plugging....a different sort of shift in response, perhaps...? 

@oddiofyl ...I was just thinking about acoustic suspension....in regards to the old AR-3a speakers.... still not the same as a passive, but closer to a defeated port...   🤷‍♂️🙄

My Magnepan LRS+ had a smaller footprint than my KEF LS50 + stands. The KEF is a bit more detailed and the LRS+ is a huge soundstage with depth. The LRS+ also have very little side wall interaction. You just need about 3 feet from the front wall. You also need some power from the amps.

I can also recommend the Studio Electric M4s, an excellent monitor-size standmount.