At least in my system, the Furman PST-8D Power Conditioner had a negative effect on sound quality.
My initial impression was that plugging my system into the Furman made music sound calmer. After several more minutes of listening, it seemed like the Furman was taking some life out of the music in comparison to both the cheap computer surge protector and the AQ Niagara. The muted dynamics and overall flatness of the sound wasn’t nearly as dramatic as with the Topaz Ultra-Isolator in place, but it was noticeable especially in comparison to when my system was plugged into both the cheap computer surge protector and the AQ Niagara 1200.
I ended up with an Audioquest Niagara 1200 with an Audioquest Blizzard power cables (after also trying a basic $15 Tripp-Lite Heavy Duty power cable and an Audioquest NRG-Z3 power cable).