Tried to have a conversation with Mr. Linkwitz at RMAF2015 about a DSP crossover that meets his challenge, but he did not want to discuss it. Why have a challenge and not talk about it?
Here is one that meets all his criteria and sounds very good:
http://www.danvillesignal.com/high-perf ... hannel-dacWorks with a PC to run the development environment to do block diagram programming for any filter network needed up to 4 way stereo. Beats all the DCX2496, moded DCX2496, DEQX 2.6P, mini-DSP and other DSP based ones I have heard. I use it in my time domain beamformed OB planar line arrays already.