B&W 801 Matrix III...which amp to use??

Ca-400 hands down. Had mine with my 801's w/Northcreeks and the sound was amazing. Had a 8008BB with them also. This amp sounded great but not near the sound of the big Classe'
Don't let anyone tell you that power is not needed. The better the amp the better the sound.

very high quality solid state - would consider classe cam 200's or pass.

Does anyone have any thoughts on a Bryston 4B ST
or a digital amp?? Or say one of the bigger Parasounds,
Rotels... Marsh...Adcom... etc..

The bigger Bryston,Parasound, Rotel or Marsh are all good choices. I heard these through a 200wpc Rotel and it sounded very good. As a matter of fact the salesman hooked up the same speakers with Krell amps and nobody could tell the difference between the Krell and the Rotel. Levels weren't matched and it was informal but the price difference was major and the sound difference was not detectable.

If you want a very in-expensive option, then try a Quad amp. Either 606,707 or 909. They have all been built for driving Quad electrostats and therefore can handle almost any load.
Dont dismiss the idea, until you try it..