I would first say that the sound quality of the system will never be very good with that receiver. I have never heard a Yamaha receiver that sounded very good.

The receivers that deliver superior sound quality are from NAD, Marantz, and Cambridge Audio.

They are more expensive, but that is to be expected because they are engineered to sound much better (and they do).

I would not expect the Sony speakers to match up well with the Pioneer speakers

If you really want decent sound, I advise you to look at speakers from Wharfedale, KEF, PSB, or B & W.