Bought a second D200 to go along with my D400

[Confused]

I think it is worth noting that a D400 will sound better than a D200, and not just because of the extra power. Devialet claim much lower distortion figures fore the dual mono, and in my experience the dual mono's sound far more detailed. So with your proposed set up you have the advantage of the D400 dedicated to bass duties, which is almost certainly a good thing. The down side is that using a sole D200 for just the higher frequencies could well in theory give an inferior performance when compared with a D400 running full range. In effect you are using the less detailed / higher distortion amp on the delicate mid range frequencies. It would be good fun trying this stuff though, and who knows might just yield some good results. One observation I would make is that I have seen a couple of Devialet bi / trip amp systems, and in each case they have been made up of multiple D400's.