Havent tried A80x series , but i own A726 & i ve been listening to it for about a year now.
Meanwhile came the Touch3g, Clipv2/rockboxed, Classic 7g, Nano4g, shuffle2g, Philips go gear (one with 2.4inch screen, dont remember model name), Samsung Wave, Nokia 5800/5233/5130, Sony Ericsson walkman 995/395/Aino.
AND you know what ........i am still listening to Sony A726
NONE of the above mentioned music sources posses the timbre, natural tone, bass depth\definition(but only in very low frequency notes), instrument placement, lower treble & finally the mighty impressive midrange of the A726.
The midrange on the Sony reaches to such amplitude levels that (sometimes my earphones literally give up reproducing them) is absolutely phenomenal.
What i dont like is the very flat & not as tight response to the upper bass( that is the sweet spot for most of the tracks) & also the lack of sparkle & extension in upper treble just as the Touch3g has.