i have the 620's, and they're ok i guess, but they have a really hyped sound to them that tends to translate as mud
i'm sure some of it has to do with my non-treated space...but as an example, i was listening to a mix i made on the 620's, and the high end sounded superb...nice sparkle to the cymbals, good "thwack" to all of the drums with lush and audible reverb tails...then i played it in my car, and it was rumble in the jungle, and it isn't the 1st time that's happened before