Since you already have the DMA-200, then it only makes sense to stay with a Spectral preamp. Spectral only seems to really work as a system. However, must use specified (MIT/Spectral) cable. I own an Aleph P and if you were starting from scratch, I'd probably point you toward the Pass product, but that's not where you're at.
Pass Aleph P vs. Spectral DMC-20
I currently own a Spectral DMA-200 amp. Am currently having some custom speakers made with all Focal Audiom drivers, custom x/o. Will also be running the big Snell sub with an Ashly pro amp on the bottom. I know the DMC-20 is somewhat of a dedicated piece for Spectral amp, but have read many good things about the Pass Aleph P (but haven't heard one yet). Haven't gotten to the interconnect/speaker cable issue yet; that's for last. Which is better for my system?