Even if you can't get ahold of the 909 monos, they're just internally bridged 909s. You could get a 909, then sometime down the line, get a second 909 and have the pair modded into the monoblocks. The process would probably be slightly more involved than whats done with the old 405 though. As for ratings, the 909 should be stable into any non-bonkers load. Quad designed all their amps to be stable into their electrostatic speakers and the 909 is the 2nd refinement of the 606 design.