Keep the DEQ which is a very good digital equalizer and with a measurement mike could do wonders. The DCX is mainly a cross-over which with your system is not needed.
This is just my thought and may not be correct but if it was me I would keep the DEQ.
The DCX crossover does have parametric EQ's, so you could get by without a separate EQ. And the DCX does has both digital and analog inputs. I have one in my system and I'm very pleased with it. I use the digital in so that I then have only a single DA conversion in the signal path.
