I think the 20 has split passive RIAA, and better pcbs, but otherwise is pretty much a DMC 12 behind the scenes.Maybe a few other changes in the implementation details.
I've never even seen a DMC 30, and this probably post dates Damien Martin's design work and participation in Spectral, so I don't have a clue what is going on inside it.
All the Spectal preamps, imho, are very clean, but subjectively a little "thin" sounding. I'm not sure why that is, but it is not likely a simple thing to explain. For better bass out of your system, it would be good if the speaker was able to be bi/tri amped, in which case you could select an amplifier which might subjectively be "fatter" on the bottom end and solve the problem that way (or even apply some EQ, gasp!).
I've never even seen a DMC 30, and this probably post dates Damien Martin's design work and participation in Spectral, so I don't have a clue what is going on inside it.
All the Spectal preamps, imho, are very clean, but subjectively a little "thin" sounding. I'm not sure why that is, but it is not likely a simple thing to explain. For better bass out of your system, it would be good if the speaker was able to be bi/tri amped, in which case you could select an amplifier which might subjectively be "fatter" on the bottom end and solve the problem that way (or even apply some EQ, gasp!).