8 ohms or 4 ohms settings for my B&W 803s?

I have a system that includes Krell SACD Standard, Rogue Audio Perseus preamp, Rogue Audio ST90 power amp, Straight wire Serenade speaker cables, Straight wire Cresendo interconnects, and the 803s speakers. I find that many cd's seam to be short on sound quality (sound sounds compressed on such CD's as Sprigstein "The Rising", Seely Dan "Royal Scam"). It was recomended that I try switching the power amp to 4 ohms from 8 ohms. Any comments or concerns out there regarding switching the impedence?