These links should help
Cowon S9 ReviewSony X Series X-1000 ReviewSony S540 Review
The B & O is a totally insane option for those with more money than sense, many due to the fact that it's cost out of all proportion for it's poor specification by the standards of either the Cowon or Sony.
Yes it's 4gb re-badged Samsung - Your essentially paying for the name, okay B&O have played with the firmware a little, but it's still doesn't justify the asking price.
The Cowon S9 & the Sony X Series players both offer better specs for half the price, when I auditioned the Beosound 6 at my local store I wasn't exactly blown away by the quality. I did however purchase a pair of B & O Earphones (A8's) for use with my Nano, as I quite liked them - LOL.
The HiFiMAN HM-801 I'm unable to comment on but if you search this forum a couple of people are complaining of SQ issues.