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!"