Using senheisser's hd598 with asus xonar d2 I can't notice any difference, so I don't worry about.

I don't know them, but judging by the photos looks like a big downgrade in sound quality. What about Swan D1010 IV, are these still too much for your desk?

I would pick the AV40. Better than Logitech for sure. I have the Logitech Z2300 and a pair of M-AUDIO's BX5, the BX5 blows out the Z2300, even on bass.

If you are using Windows, the best way to rip is using Exact Audio Copy. *http://blowfish.be/eac/Caaok/caaok-eac-1.html Using sox to de-emphasize, edit sox batch file to something like "sox input.wav output.wav deemph".

Quote:   Is there any difference compared with the original cable besides the direct 3.5mm ?

There is also the Xonar DGX, which has headphone amp. I have read that in terms of sound quality the DSX is a bit better than the DGX. There will be a difference between the onboard sound for sure, but I don't know how big haha.

If the 555's bass is not enough for you, the 598's bass probably won't be too. Someone correct me if I'm wrong here, but the 598 has a bright signature. I really enjoy these headphones, but I'm not a basshead. I think that your Xonar DG is fine for the HD598.

A good mastering makes much more difference than the audio file being lossless or lossy.

Quote: yes

Quote: Kinda, if you scan a single track as a single album or a single track, the volume adjust will be the same.

I would select all songs and "scan selection as albums (by tags)" through foobar2000. Scanning as albums will preserve the album tracks original volume differences, it won't have much difference between single tracks and albums though. Try to apply replay gain as single tracks to an album...

foobar200 here. I used to use itunes, never missed itunes after moving to foobar.

ASUS Xonar D2 with HD598 sounds perfect to my ears. I had the some kind of doubt once, but I never tried something like an E9 because I already had the Xonar D2. I don't like to keep switching cables everytime I want to use heaphones or speakers, though.

I'm using the HD598 headphones with a Xonar D2 soundcard. It sounds good to me. How much a FiiO E7 for example would improve the audio quality ?

foobar2000, with LAME (if you want mp3)