Speakers sound too bright.

For everyone pointing at the room, I tend to agree that is a weak link. But the OP has stated that the KEFs didn't exhibit this behavior, so the room and the equipment are the constants in this scenario. Room treatment will certainly help any speaker perform it's best, but that might be the primary issue here.

I would also recommend letting the woofers loosen up through break-in time.  I bought a used set of B&W 805 D4 speakers that were super bright with little low end.  I solved it by adding some wall treatment but mostly by adding in a Schiit Loki Mini equalizer.  Big difference!  Just $149

Hey guys, appreciate all the feedback. I’m soaking it all in.

something interesting last night, I checked the polarity last night and my left speaker was positive and the right was negative. Everything was plugged in color coordinated between the amp and speakers. Should I swamp the right speaker inputs to achieve positive polarity?

Greetings,

Sounds like speaker break in is important. 
Question is the best way to do that. 
Your advice is greatly appreciated. 
Someone noted placing the speakers facing each other 24/7 for a week.

If so, how much space in between them? Maybe it doesn’t matter. Is as loud as possible recommended?

Thanks to all. 
 

Square room doesn't help the situation.  Change what you can, speaker placement, acoustic panels, rugs furniture room treatments, seating location.  Here's a good article for understanding room acoustics; https://realtraps.com/art_room-setup.htm#:~:text=THE%2038%20PERCENT%20RULE,-The%20placement%20method&text=This%20offers%20the%20best%20compromise,back%20from%20the%20front%20wall.