Cornwall IV and subwoofers

That speaker big pile chip board and plastic. Buy Maggie or Rockport speaker and and give your ear real treat.

Svs 3000 series tons of great reviews and by owners 
and all adjustments including volume all done with their great tablet,or phone app,
and sealed is always preferred for audio ,much more accurate .5 year warranty free shipping ,45 day audition ,not many 
can compete with that.

@tubebuffer I could not agree more about the rockports. I went from Magico S1mkII to Atria II and could not be happier. They do cost $21K more so a different league all together. 

I’m using a pair of S/510 from REL. I auditioned the CW4 and S/510 together with my amp before picking them up. Definitely improves the soundstage and overall experience.

Connection is speaker level.

I am amazed that you need a sub with the Cornwalls. I have Tannoy Arden Legacy, also with 15" drivers definitely no sub required.