Hmm, these headphones sound entirely different to me. The HD600's have alot of bottom weight, and have a tighter soundstage. The bass on the HD600's sound more like two subwoofers close to each ear (in terms of impact), and the high end sounds naturally rolled off. Great midrange detail.
The K701's have full, deep bass that fills a huge airspace without having slamming impact. The midrange is textured, but not overly apparent. The treble has much detail, sparkle, and you can feel the the treble reaching for the stars. Not the warmest, but it just throws out lots of detail and a HUGE soundstage.
I didn't think they sounded anything alike, but if you don't like the 701's too much, the HD600's may be perfect. The thing that eats at me over the 701's is it's all in the amp synergy. They are completely different headphones on different amps.