My new set of QP400s showed up in the mail yesterday. For those of you who don't know, MB Quart was a German company who was closed down and moved to Japan a couple of years ago. Engineers started a new company named German Maestro which is now the equivalent of the original MB Quart headphone line. The QP400 was their flagship headphone and is more or less equivalent to the German Maestro GMP450 and the Charter Oak SP-1, an re-branded version of the headphone.
My roommate has a set of SP-1s and upon early listening, it sounds like the QP400s have a more powerful vocals and a wider sound stage, while the SP-1 beats the Quarts in speed and instrumentals. Both are outstanding headphones, nonetheless. We are planning on writing a rather sizable thread/review/comparsion on the two upon further listening, hopefully including some specific songs as well as overall impressions.
I would love to hear the GMP450s to compare even further, but that does not seem feasible right now. Anyway we will need to do much more A/B comparison before saying anything further. If anyone has heard any of these I would love to hear your opinion as well!