I think the key is the DAC. People on the SB forum give mixed reports on a power supply upgrade. From great to no difference at all. The only guy I read who actually did a single blind test couldn't tell any difference. I built a very nice 3A linear supply, if it helped it wasn't obvious. I haven't tried a blind test.
I just read about a study done in the UK on people who claim to be made sick by cell phone tower radiation. They were right, sort of. The researchers found that if these people thought they were being subjected to trasnmissions they became sick. It didn't make any difference if the tower was transmitting or not. They just had to be told it was. Additionally, in a double blind test they couldn't tell if the transmitter was on or not. I think a big part of high end audiophile cult follows this same pattern. But then, hey if you are enjoying it more, good for you.