JBL specs the bass in an anechoic chamber so their specs are so different than typical high end audio exaggeration.
I have measured flat to 35 hz in a gigantic room of 50,000 square feet!!! A generous sized listening room of 14 x 24 x 10 is 3,360 cubic feet. In a normal/large living room I have seen them go flat to 22 hz. They are very serious in the bottom end. The 67000 goes to 33 hz flat in my giant room.
I've heard the Kingdom Royals in several rooms, I like the Canterbury and Westminsters better.
I would go for good tubes on the Everests if you get those. 100+ watts would control the woofers well. Remember, those are 2 15 inchers per side!
The right lower powered amp would work too, but it is unpredictable which lower powered tube amps will make the woofers go and which won't. Specs don't tell.