I have owned (still do) 804s and 803d B&W speakers. I use them with Parasound JC1/2 SS amplification and I do find they are low impedance and power hungry. I find they need to be set up well into the middle of the room away from any walls. This reduces bass response somewhat so I supplement with a HSU sub.
The transient response is fanatstic in these speakers (if you have the amp power to drive them). Forget tubes IMHO unless you listen to chamber music at very low SPLs (or you have a megabucks/high power tube amp).
I have found the "d" version to be a bit bright on some program material such as flutes, high pitched female vocals, some horns/sax. Sound field/imaging can be very 3D depending on program material. Some material (like older rock) resolves into a center image and two side images focussed at the speakers. Maybe I have mine too far apart, but I set them up to minimize the upper midrange re-inforcement when they are too close together. They have execellent resolution, as I have heard/resolved sound like vocals/lyrics I had not heard before on other systems.
A note about hearing these in a shop. I have never heard a pair of B&Ws in an audio store showroom sound as good as when properly set up in your own home. This I think explains some of the love/hate response to these. I bought my 803d from a Bay Area shop who is an avid B&W dealer, yet they still sounded bland with flat soundstaging in their shop.
They also benefit considerably by using a solid wood plinth with heavy brass footers. These clean up much of the upper midrange brightness and tighten bass response considerably.
I think the mid range (804/803) versions are an excellent deal used. Not so much if you are paying full retail new.
