Before you spend a dime, optimize your speaker posistion first. This will have a greater affect on the tonal balance than any pc cord.
Neutral to Lean Power Cord for tube preamp
I recently added a deHavilland UltraVerve preamp to my system. It is quite powerful and dynamic, but has a little too much bass emphasis through my Von Schweikert speakers, driven by a McCormack DNA-1. All cables are silver, using a VooDoo power cord now on the preamp. Everything plugs into a PS Audio Quintet on a dedicated line. Looking for a very neutral, or slightly lean more detailed power cord, price range is up to $400 used. I am still tube rolling, so bass may get tamed a bit more yet.