According to gsmarena.com the HTC one has equal or better SQ than iPhone 4/4s which is what i've used as portable source, can't wait till someone here get's it and we get a decent audiophile review for it.
hey Im using the ONE SV,which virtually has the same sound quality if you look at the GSMArena review,and Im using it with powerAMP app,as the sound quality in the stock player with beats enabled sounds similar to my brother's 4S,which to my ears sound boring and flat and quite annoying.
so yes,the sound quality equals to the icrap...ohh sorry iphone 4S...:)
I would download to your PC first then transfer to the HTC One. You may want to listen on your PC occasionally and it's good to have a backup. Additionally, if you keep reading this site, you'll be convinced you need a full desktop system, another DAP or two, perhaps another headphone, etc. PC is a good base camp for transferring, converting files, ripping CDs (gasp!).
Plus, you'd have to have a pretty good data plan. Files are large.