Well, in conclusion. I now have a back wall partially covered in monster bass panels and this has made a big difference. However, the one thing I have come to realise is just how fussy these ATC 19s are and how much they interact with the room (I have no idea why). First I moved the (digital) piano. That was a revalation and removed a lot of boom. Then I increased the toe in to great effect. Then came the panels. Using some as corner bass traps made the atcs sound so lean I could barely believe it. I wondered if this was the sound that some people have achieved that has put them off ATC. With all panels back on the back wall the issue was overpowering lower midrange and particularly female vocals - I really like Ameliana Torrini but she was giving me a headache. Toe in reduced again and result! I have never had such fussy boxes in this room and I've had a few. So no, it wasn't the amp (which I actually really like now). And with other speakers it's probably not simply the room. As much of a pain in the posterior as these ATCs are, they are great when positioned correctly. It's been a bit of a marathon effort, but all seems well right now. I could have easily spent a lot of money changing equipmen. Thats what I've done in the past perhaps unnecessarily and I'm sure that's what often happens to other people. ATC told me room treatment and correct positioning would be the biggest upgrade possible. They were absolutely right.