I used to have the K702 and Q701 but much preferred HD800. The detail-retrieval and soundstage on the HD800 was noticeably superior. I'll give you the midrange may not be as enjoyable as the AKG's but that can be fix with a Sophia or Sylvania 2A3 tube.
Right now I have the stock tubes in with the RCA rectifier. I'm getting ample soundstage with the HD800.