Is your system still Analog if you use any form of DSP?

You are losing sleep over this question?

Ask Mobile Fidelity about that.... 

If you are using a pure analog electronic crossover, it is still considered an analog system. However, if you apply DSP after the DAC (which seems to be the case), there are additional A/D and D/A conversion steps involved inside the DSP processing. In that case, it is no longer a purely analog system, even if the chain / system looks like analog. This is a passive crossover system.

If you process the digital signal using DSP and keep it in the digital domain all the way up to the final D/A conversion and amplification stages, you have an active crossover system that will likely perform best when properly implemented.

If you have a 2 channel analog system, there's no reason to use DSP to integrate subs. You can if you want to, but your best option is to get a pair of subs that are intended for music, not home theater, and use the speaker cable inputs to get the signal to your subs. If you have a HT system, this may not be your best option, but it sounds like you are just listening to music.

@lewm 

I do not loose sleep over anything.  Just a question.  I would think that adding 4 RCA connections and another device in the signal path would have more adverse effect that the DSP processing itself.