A transparent, easy to use (remote) multichannel (not just 6 ch, like 16ch) attenuator.
A modular programable DSP/hardware crossover unit that is affordable. Say for 2ch stereo, you have 3 ways. The input accepts a digital or analog input and you have have 6 outs ( 2x3). This is much like the DEQX, except without the proprietary software. If I use LSPcad to design my xo filters, I can plug those in. If I use SoundEasy, I can plug those. If the manufacturer of your speakers has a filter design that he intended, he can provide his and you just enter in your filter into your active xo and away you go. If you upgrade to 4 ways or add a sub, plug in another module to handle the additional outputs, or if you want to go multichannel, do the same. Then the above attenuator handles the volume problem, but this could be a seperate box IMO complete with buffers for driving the amps.