surteess,
I tried 4 Pioneer CS-05 round speakers on my Sandui QR-4500, and took two back, and went for a pair of Sansui SP-2500 for the front A channels, keeping the remaining pair of CS-05 for rear channels use only.
I wish I could have kept the extra pair for the B side rear channels, as they have everything but floor shaking Bass response. Who would know back in 1972 that they would later add the power sub-woofer, but frankly, the ones that I have heard are not that good, as a mono source of good bass sounds annoys me. Setting those SP-2500 on the floor, in some room arrangements, to appease others I have had to stack the CS-05 on top of those from time to time, or outboard of them Then I could only use them as a B Front pair instead. I had Bose for rear speakers, matched pairs. That is where the Sansui A-B Stereo pots best come into play to adjust for room acoustics. All in all, I prefer the Quad arrangement pictured above, on the A speakers only.