Full range speaker recommendation

Sonus Faber Lumina Vs should work well in that space.

If you want to keep a form factor similar to the ATCs, Spendor Classic 2/3s will be fuller sounding than the ATC's.

Lastly, as a total alternative, it's worth giving consideration to Magnepan (Magneplanars) - they might lack a bit of punch on classic rock but they are superb speakers.

Following johnto’s comment and responding to an earlier poster, there is absolutely no reason why a pair of Magnepans will not work in that room.

Separately, (Saul Cohen), it’s not that the Watt/Puppies are difficult to place, but they require very patient and accurate setup. However, you could still find them a mite unforgiving tonally.