The kind of difference you describe, lol999, is tough to assess because some answer these questions in night-and-day terms ("The heavens parted when I substituted the Gonzosonics Rubidium power cord") while others say they are BS. There seem to be few differences everybody can agree on, but you have to get there (or close to there) before I consider a difference to be "night and day". In other words, a difference which can be picked out by anybody and/or in blind testing (which is largely shunned by the audiophile community). Personally I think that while there may be differences, they are dwarfed by (and, in many cases, masked by) the nonlinearities in transducers. Putting small differences in 'night and day' terms clouds the issues IMHO.
If you are running your Pi into an external, self-powered DAC, I'm in the 'whatever' PS camp. If using one of the bolt-on DACs that shares power supply, that's a tougher question.