Be careful of that foot tapping thing. This sometimes is caused by strange frequency and dynamics anomalies which lend a sort of rythmic monotony to the music. I think some Linn equipment has this designed in.
Anyway, I use one major criterium for new components - does it make me want to be in my listening chair (sofa in my case) when I'm actually doing something else? Does it make me think with pleasure about that time of the evening I can again listen to music? Does it cause me to, when walking by the room, stop, gaze in, admire the system, and say, "Damn, I love you guys!"? And does it cause me to jump up while listening and find out who's playing that clarinet, trumpet, guitar, etc.? (I do that a lot lately because of all the wonderfully fine transfers of great jazz recordings of the last 60 years.) And finally, does it cause me to take CD booklets to bed as reading material instead of Sterophile, TAS, etc.? (Again, those damn jazz, rock, and classical reissues. Just picked up Cal Tjader's "Soul Bird" on 24/96 Japanese import today.)
Oops! Guess that is the required five criteria!