I don't listen much to Blues, but I listen mostly to Classical and Jazz.
I think for the person who is not critically listening for every last detail in every recording, the HD600 is a great recommendation.
It will produce great rich, textured tones and have enough punch in the lower mids and bass to really give the bass drum or upright bass a serious presence.
I found that they slightly pull back on the extreme highs.
If your listening tends more towards the neurotic extreme detail cravings (like mine), you'll want the DT880 / 600 ohm. It doesn't have the beautiful, luscious, resonant warmth of the HD600, but it is as clear, clean open as anything I've heard. It's a very neutral (some might say cold) HP, with amazingly brilliant highs and mids.
They both will benefit from a good amp, but it really depends on your tastes and more so what you want to hear in (or out of) the recordings.
On another note... (pun intended). If you listen to compressed tracks (MP3's at 128k, let's say), you'll be better off with the HD600 as it will smooth out the rough edges. The DT880 will reveal everything (pretty and ugly) about the compression (as homeros8000 said about the 701's).