So I've been using and really enjoying my current setup (E7/E9 -> M50/DT880 600 OHM) for a while now, but I feel the need to move up. I have a variety of ideas, but I'm looking for some advice on both what options to go with AND which piece to upgrade first. I enjoy most types of music, but prefer highly detailed, clear reproduction. Current thoughts for headphone upgrades are HD600/650, K701 (I've heard and really like the 701, but is it an upgrade or side-grade?), D5000, and HE-400. Amp wise the only things I've really thought about are the Schiit Asgard (with the E7 as DAC until I can afford the BiFrost) or a Little DoT MK-something.
So, fellow head-fiers, what might you suggest for the best first step to be?