I currently own a N97 it looks like the N8 is using the same chip as it has exactly the same frequence responce etc as the older n97, the n97 sounds fantasic but needs a amp to drive anything 12ohm it's really weak, but the quality of the sound is fantasic, the sound is really crisp/clear it has the crisp and clearness of a £200 amp, it's also very netruel and like the graph suggests lacks a bit of low bass the soundstage is quite wide and you can clearly pick out individual sounds easily with a decent set of cans, once you pair it with a amp to bring out the bass and give the sound more power/fullness it sounds really very good, i use my n97 with my fiio E7, the E7 brings out bass and gives a slightly more fuller/powerful sound while retaining the oringal crisp/clearness.
I would highly recommend the N97/N8 as a portable player if you enjoy a really crisp/clean netruel sound but if you plan to use anything above 12ohm with it you would definitly need a amp.