bo1972 the only thing you can pick on is stage depth? In my experience, I sold and installed high end audio for 9 years, the perceived sound stage of a system, depth, width and height, was much more a product of the environment and set up than the actual speaker design. Physics is a science that you cannot overcome, a two channel stereo system only has two point sources, they are generally set up in the same plane so as to give a balanced image to the listener. For the purpose of this conversation we will limit the comments to speakers that radiate in one direction, when you get into dipole and planar speakers it is an entirely different conversation. That being said any perception of stage depth, width or height is an illusion painted by the speaker.
Most people are best advised to purchase a speaker for the tonal characteristics and range they can reproduce. Then, with
competent
professional help, get them set up properly in their room for their particular desires. Everybody has different experiences and references they use when comparing systems. For example take two audiophiles that have tickets to the same symphony, in the same hall and the same night. One has tickets in the third row of the orchestra section, the other at the rear in a balcony. What they hear and what they find critical to reproducing that live concert experience will require different home stereo systems. Consider they most likely have different home listening environments and budgets, their respective home systems will not be the same.
Speaker manufacturers go to great lengths to insure phase and time alignment of their products so the signals from each of the individual drivers making up a speaker system arrive at the listeners ears at the same exact time. B&W designs their products to be more forgiving in the various environments they will be used, no two rooms are the same. My experience has shown me that outside of speakers that can be adjusted for the environment, like Wilson Audio, B&W are more forgiving of their environment than other brands. In regards to sound stage I have found that adequate distance from the wall behind the system is critical when tuning the system to the room.
Regarding power amplifiers, the others on this forum are correct, B&W speakers are relieving enough that every amplifier, and I don't just mean different brands, but each model within a brand, will sound a bit different. In addition the upstream components and cabling are also factors that will influence the sound. My experience is that B&W speakers like as much power as you can give them, no matter how loud you like to listen. You can easily justify the cost of mono block power amplifiers as well as bi-amplification if you so desire. You might like the sound of two 300 watt mono amps better than a single 600 watt amp in your system.
Please keep in mind, when dealing with high power amplifiers the electrical system in your house can be a limitation. If you live in the USA, with 120 volt service, you would a dedicated 20 or 30 amp outlet/breaker for each amplifier. Some companies even recommend 240 volt service for their larger amplifiers, e.g. Mark Levinson and McIntosh, and offer 240 volt/ 60 Hz versions for sale in the USA. there is nothing more frustrating than a few of hundred of dollars of electrical work limiting your $100,000 system.
Classe and B&W are part of the same corporate holding company, and B&W uses Classe electronics when developing their speakers. I have heard it said B&W "voiced" (like a concert piano will get fine tuned) with Classe electronics. Because of their corporate kinship Classe would certainly be a great starting point.
I once sold 4 B&W 802S with McIntosh electronics to a well known concert pianist. He wanted a speaker in each corner of his conservatory at his house where he practiced.
I can here the collective gasp form all you purists. He wanted to achieve the illusion of being in the middle of the orchestra, just like he experienced when he was performing. that was the way he was used to hearing himself. He also had his piano "voiced" to compliment the speakers. I had a chance to hear him play with the system as accompaniment, it was an unforgettable experience.
One last piece of advice to Matt, the home listening experience is all about emotion. You should try to have your system bring back the emotional component of the experiences you are trying to recreate or simulate. Striving to reproduce music exactly as it is experienced live, particularly in acoustic performances, with different point sources for each instrument will drive you to drink, abuse drugs, and end up in a unstable emotional state like bo1972.