The process of evaluating active crossover units has been revealing. My findings briefly are:
1. Instant switching is critical for evaluating subtle differences.
2. Digital active crossovers may not be compatible with tube preamps. Some attention is needed regarding gain structuring.
3. The units were comparable regardless of price - the differences could be picked by some and not others. This would suggest they are quite subtle. (Note - we did not adequately test DEQX so it is excluded from that comment).
4. All the units were transparent enough to satisfy the majority of DIY speaker enthusiasts.
If you have tube preamps and power amps, then you may have trouble with any of these DSP units. You could use MiniDSP as a development tool and then have an analogue crossover made up. Or you might find a solid state preamp gives better results.
Sonics vs features
In a test like this, attempts are made to level the playing field. In an actual system, they will all sound different as they have different filtering options. DEQX allows steep filters up to 300db/octave as well as advanced time and phase alignment options. DCX only allows textbook filters while MiniDSP allows advanced custom biquad filters. The modded DCX has a remote control. DCX has an auto align feature for time alignment, while with MiniDSP this can be done manually.
In general I would tend to recommend MiniDSP as the first low cost option to try.
More about DCX vs MiniDSP >