OK, so the X1 is
a separate crossover module . Crap - disregard at least my first suggest. This is a fairly atypical system - the 55 page
manual covers their Evolution system in general, including how to assemble the various tower speakers and such. If you are using NHT towers with the unpowered sub in the base, your best bet is to go with the NHT recommended approach: mains set to large, sub set to LFE, mains and sub pre-amp output all connected to the X1, left/right outputs of X1 connected to 7125, and sub output of X1 connected to A1 to power U2 modules and left/right subs.