805 S + Sony STR-DA 6400es... what next?

I am probably going to be riped for purchasing a Sony and wanting to use an all-in-one but here I am...
I just purchased the STR-DA 6400ES, and am hoping to pick up a pair of 805 S' in the next week. I listen to a range of music to include rock, jazz, blues, and r&b. I have a small place and the system I am hoping to put together will equally be used for music and home theater. I want to keep it simple and do have a budget. My eventual goal will be to build a surround system; for now just a two-way.
Do I need an amp for the speakers...??? How much power...??? Any advise would be appreciated.
You should use the 805s'with the Sony for the time being. It may be entirely adequate if the power ratings are honest. As for quality, you are the best judge.

I would recommend auditioning these speakers with a different amp/pre combo. Even a Rotel would be a different world of sound for this level of B&W's.
Most Sony, even ES line, tend to sound harsh and un detailed with real speakers like B&W. I have a set of 804's and used to drive with a Yamaha rx-v 1500 receiver. Now am using an audio research SP-16 pre with a 20 year old Krell KSA-250 and listen to the stereo for hours. Bass is no defined and effortless Highs are now open, have depth and are detailed. If you have the money, its worth a try, you can always sell the equipment.
yeah man Basque23 is right, Ditch the Sony.
Using it with those B&W 805's is like putting a diamond on a brass ring. Time to play with the big boys. Get yourself a nice power amp and separate pre. and don't forget to upgrade the CD player and cables too. (no more monster cable) Believe me, you'll hear it and know what I mean when I say "it's worth every penny!"