I was just about set to make this purchase, then I discovered via the online manual that the 520 only allows for a variable crossover point for "small" speakers of 80 or 100 hz. My concern is that the polk rm-6600 set I'm using have an internal highpass filter at 150hz(according to the polk forums). I would run the front speakers through the sub, per polks suggestion so I wouldn't lose anything there, but I'm concerned that for the center/rears I'd be losing 50hz. Can anyone confirm or deny this? Would it be a problem? Am trying to make a purchase in time to get it for Christmas, but keep getting minor setbacks. Appreciate any and all help.