that's all well and good, and scientifically measurable, but is it really audiable (all things being equal (ie level matched as seen in richard clark's amp challange)? i know rc's amp challange get's used as an example all too often, but why not? it's been going for years and afaik no one has gone close.
imho you're better off buying an amp with the features you need/want (power output, adjustable filters, brand association (read record of reliability, and resale value), cosmetics etc. your money could be better spent on installation than on inaudiable differences.
This issue has been discussed at length in just about every audio group and usually ends up as an "I can hear the difference, you don't know what i hear so how can you say i'm not hearing a difference" Vs. "There is a measurable difference; but it's beyond the threshold of hearing".