I just bought a MX 5.1 and a prestige S10 Subwoofer. I hooked them up via Y adaptor to my receiver. Since you already have 2 mirage subs maybe you can answer my question. Does the blue power light stay on when in the "auto off" mode? Any information would be awesome. Thanks.
As for the crossover question I always play with the settings. I start at what the manual says then go +/- 10-20 Hz. Mine says it should be as close to 120hz, so I just play with it to see what I like as long as I'm in the ballpark.