Which makes the bigger difference?

Given your speaker setup is as good as possible... and so forth... the biggest improvement in sound staging, and imaging results for me came by way of going to mono blocks. Tube or SS. First was SS twin mono's on one chassis. Super. that was followed by actual separate twin mono block tube amps. Better in many ways, but they don't match the presence the big dual mono stereo SS amp provided.

Each instance was channeled thru one of two tube preamps in SE fashion. Although the tube monos don't provide the immediacy of the SS amps, nor the bass impact, I do enjoy them equally well... and I am continually torn between the two distinctly different sounds each presents.

the best situation? having both tuype amps is clearly the way for me... and just switching back and forth from time to time as the mood indicates.

having both available, I am not intrigued sufficiently to bi amp my speakers with them either.

Thanks to everyone for thier thoughts, I pay ALOT of ATTENTION to vibration control and Room Tuning has made huge differences, as well as other small things such as great cables, cable elevators and PS Noise Harvesters. I've got a small room so little adjustments produce (sometimes) profound differences. Just wondering about my gear, I'd like to go to an ARC CD3 or maybe a Jeff Rowland Integrated (if I can muster the funds) but that's why I ask the question of impact and from what might the best logical choice if I were to make a change and if to go to seperates.

Sorry also failed to mention my interest in the Bryston CDP1 and the Sim Equnoix SE as a possibile match up as well

Agree with Krysgel, your question is about which change in electronics will get finer detail resolution, and isn't about changing speaker or room. Looking at your system as listed I think I would look at a CDP upgrade.