I ran the Quatro's for over 4 years in a 15' x 11.25' x 8' room and they worked really well once I spent the considerable time to dial them in for room placement and then adjust the bass equilizer for finishing touches.
They worked very well with an EAR 890 that pushes 70W class A tube power with a lot of oomph. I liked them even better with a 100W VAC Phi 200 driving them. I actually used my Primaluna Dialogue One for a short interim fill, and they sounded nice and musical, but were not powerful enough for loud rock, big orchestra, electronica, etc. It is a EL34 based amp with 35W, and I would bet that KT88 might work a smidge better. More power was better, though.
I would seriously think of a more powerful amp if you like concert levels of louder music.