Why Expensive power Cables when Romex behind Wall?

Boros: You have just put your finger squarely on the issue that many audiophiles with expensive power cables really don't want to admit: why invest a lot of money in a power cable when the electricity coming from the wall has just travelled hundreds miles, maybe even a thousand, through commercial power transmission facilities, been through umpteen transformers, and then traversed home wiring on the other side of the wall plug that is, at best, barely adequate? Unless you upgrade your home wiring with a high quality dedicated line, "gilding" the last 3-6 feet of the wiring with a $250 (or more) power cord doesn't make a hell of a lot of sense, does it? About the only rationale for doing this is to get a power cord with shielding/RFI filters to minimize RF interference, assuming you have such a problem.

I believe Sdcampbell is correct. At least to a good extent. I had a demo'ed a few power cords and owned a Cardas Reference power cord which came with my amp and is/was a decent middle of the road.

I ended up demo'ing and then buying three (one for each component) used Foundation Research in line power conditioners, LC-1's and an LC-2. These in-line power conditioners replace the power cord and IMO do far more to lower the noise floor, enhance 3D soundstaging, and sibilants and cost about the same as some good power cords.

That would be my recommended route.

BECAUSE there is a low grade cable behind your outlet and because it works. You don't question why a water filter works after your tap water travels 100 miles through some nasty pipe, it is similar with good power cords although not exactly analagous. Some people think that the power cord is the same as adding a few feet of pipe to an existing pipe, but such a pipe simply would not impede water flow, whereas a power cord can improve signal flow, filter grunge, lower distortion due to better grade materials. Just try one under $200 that can be easily resold if you don't like it. One audition beats a hundred debates in the posts. SD I respectfully disagree based upon personal experience, having been skeptical myself.