I swapped out the stock cable with a Nordost Purple Flare power cord. There were some minor improvements. The sound seemed weightier, smoother and more natural. It's also slightly easier to identity micro details in a track. Overall a nice upgrade.
Wow. that implies there is some power filtering missing from the iPower and the pro iCan. I was under the impression the Pro's power handling is really good an not affected as much by power input. Then you add the iPower, which is also supposed to clarify power quite a bit. If some as basic as a power cord can make a difference, I'm very skeptical about the claims from iFi on the efficacy of pro and iPower's ability to provide clean power.
Have you tried multiple blind tests with a second person to make sure you aren't just suffering from selection bias?