I believe that the main attraction of the MRA-D550 is that it has fiber input and does its own 5 channel decoding. These features are already built into the H701. I would be more inclined to buy a decent higher power 4 or 5 channel amp and let the h701 do the decoding. The d550 doesn't have any line level inputs I don't think it would prove to be very flexible over time.
i thought dcondors talkin about the new alpine amp thats 1000x1? isnt that the MRA-D550 ..if so i been meaning to try one out. i might get one n hook it to my 12w7