Speakers for a Krell Vanguard

Just picked up a used Krell Vanguard to replace my 23 year old Krell KAV 300i (It’s getting old, like me, so I thought it was time for a change.) It is powering a pair of Thiel CS 2.2 speakers (also 23 years old.) I would appreciate any suggestions on speaker improvement. The room is a fairly large rectangle with little in the way to absorb sound. It houses the living room on one end (2/3) and kitchen on the other 1/3.) all of my cables are high-end. 

The new Vanguard has improved the sound of classical orchestral pieces, which were a bit muddy sounding with the 300i, and added a bit more shrillness to some of the pop and jazz pieces I play. 

For any of you out there with a Vanguard, I would appreciate any suggestions to improve the sound; either different speakers or additions to my Thiels (like a subwoofer) that you think would improve it.

I had a friend who just sold a Vanguard.  He was running it with Focal Arias and a subwoofer.  It was a good match.  The Arias lack the brightness of the higher end Focals with the BE tweeters, yet sound very good.  You could also look at Monitor Audio Silver or Golds depending on your budget. 

Good luck