The situation is a bit more complicated, so let me explain first. At the moment I have a pair of HD 555 (had them for 4 years) and using the onboard sound from an Asus laptop. It's pretty decent, and it was a blast the day I received my headphones after being used with Creative and the likes. Until now I've been very satisfied, but I feel it's time to change my headphones since the sound has started to decay a bit (less bass, highs are a bit rough, less power, etc.).
But first and foremost I'd like to find out what's the limiting factor. Whether I should stick with the onboard sound or if it's worth investing in an external DAC, such as the Fiio e17 or other suggestions. Sound level was never an issue with my current system, so I am mostly interested if there is a benefit in the quality.
I mostly listen to rock/hard rock/alternative/electronic, no hip-hop,pop. I prefer a richer sound with well defined mids/highs than loud bass, but some degree of bass is necessary. Sources are either flac or 320 kbps mp3. To be honest I haven't been able to notice much difference between 320kbps mp3 and flac (I assume it's because of the onboard chipset and not the headphones/ear, but I might be wrong). The sound tends to distort at max level, feels somewhat dull and there is some background noise, especially at high volumes.
And speaking of headphones, is the 598 a noticeable leap in quality compared to the 555? Or any other suggestions in that price range. I prefer open headphones and I am a little biased towards Sennheiser (don't hate), if not for the sound quality alone, but the fact that they lasted so many years while taking a lot of punishment.
I am in UK and the price differences between USD and GBP tend to vary a lot. Budget for DAC (if needed) - £100, and headphones - £200. I'm willing to push my budget if the improvement is worth it.
LE: Corrected to 598, sorry for the typo.
Edited by fireblast - 1/31/13 at 3:56pm