I'm a big believer in science. What really matters in a power cord is that it carries the current to the amp. Heavy gauge wire is a must, along with good quality connectors for reliability. There's a small company in NJ that makes really nice cords, and I bought a pair for Cherry MONO demos. They are also very flexible which is nice when you need to swap out components. I have a Pangea 9-gauge that's just too hard to maneuver sometimes, but I trust it to be the strongest connection to the AC mains possible. You can sometimes hear the difference but it's really a tweak unless there's something bad about the cord you're replacing.
As far as power conditioning, the Cherry amp is designed to tolerate large fluctuations in AC mains voltage and distortion. Some line conditions have caused problems for our customers, such as one from PS Audio that actually "boosts" the voltage so much that it trips the over-voltage protection in the amp. The other issue is power output since handling peaks can be difficult even for high power conditioners.
In most cases, you should try out these things before committing to them. I'm also a believer in the psychosomatic improvement. A friend of mine bought $2500 speaker cables once and we spent half a day on A/B comparisons. I didn't hear any improvement, but he swore he did. I'm pretty sure he was pre convinced based on the cash he just spent.
-Tommy O
