Well, I am a cable believer myself, but I agree that it does not make a drastic difference in SQ. I personally believe from my experience that there is no substitute to hardware upgrade if you wish to go a step higher.
In my limited knowledge I have never heard a power cable change the tonality of any equipment, but it does brings in more clarity, improves soundstage and add some amount of clean dynamics. I personally believe that any power cable that changes the tonality maybe faulty as it is now supposed to do so, but only give cleaner current to the gear.
Although, I must add that interconnects does tend to bring about change in tonality (in this case I have played around with plenty).
Coming to Monkey's question in the REF1 thread about Kingwa's belief in power cords, its true he believes that a good quality cord does tend to bring out the best out his gears, it is like sqeezing out the last few ounce of goodness. But at the same time he also believes the best way to upgrade is the hardware way, which is why he personally uses the not so fancy cords he has made himself.
For example a DAC19 with cord costing a grand will never sound as good as REF1 with normal powercord that comes free with REF1 (both combination nearly costing the same) .. IMHO.