What's next for the ultimate sound quality?

Right. So the consensus seems to be to leave the speakers be and upgrade amplification + install sound panels.

If tube amplifiers sound as cool as they look, then I'm sold :) It also seems possible to build one yourself and stick to the DIY philosophy. I'm afraid the richness of sound also means "warmness", no? In this case, tube amps may not be the best match for the warm scanspeak drivers. I'm going to try a tube amp anyway. Also, browsing a little online about Krell 400xi, it seems that it's kind of bright, revealing and aggressive, which is exactly what these drivers need imho. Definitely something to try!

So many thanks, everybody!

The system sensitivity is around 92-93db. The tweeter is 92.5 and woofer is 87, but since there are 2 of them wired in parallel facing the same direction, you get +6db = 93db for the woofers as well.

You describe two shortfalls: soundstage and imaging and thin sound.

The soundstage and imaging could be improved with the acoustical treatment as suggested by Mdowns32. You are probably getting alot of sound reflection which blurs the image and soundstage. Also, make sure that the speakers are equi-distant from side and back walls. Also, play with toe-in angle.

Thin sound: You might try putting the speakers closer to the corners or at least closer to the back wall.

Other than that, you are into trying a number of things including different amplification - I have always preferred tube and there are a number of different designs using different driver tubes that can affect the sound. I have gotten the impression from reviews on digital switching amplification is that it can sound thin. You might want to try different cables. Good power cables can make a huge difference. The DAC recommendation is also very valid. Finally, controlling vibration and resonance is also important.

My suggestion would be try to locate the closest audio society in your area, listen to different set-ups, and possibly borrow equipment from other members to see what the effect is of different equipment, cables, etc.

You will get a lot of good recommendations from the Audiogon forum but it comes down to gaining experience with different types of equipment - solid state, tube, and digital switching amplification; effects of cables, effects of good transports, effects of vibration control, and so on...

Good luck and enjoy the journey!

If you go with a kit for amplification, check out the Audio Note kits.

I bought a used Sugden amp here and it makes an astounding difference in the sound of my speakers. Extremely warm, natural, beautiful. The sound from my Denon receiver is nice for video or background music, but never for critical listening. It sounds thin and forced. A good amp will let the music just flow, and when you close your eyes the speakers will disappear.