Wojc, Please keep in mind that speakers do NOT HAVE WATTS. A 400 watt speaker? nearly meaningless, except to marketing types. Unless you are reffin' ONLY the subs amp power. Of more importance, given the powered sub, is your crossover options. Are you 'stuck' with the AVRs settings or can you run a full-range signal TO the sub and use ITS crossover?
Magnepan MG1.6qr HSU Research VTF-2 MK3 2x Parasound A23 Parasound P5 Cambridge Audio DACMagic Plus Sony PS3 x4 @3foot runs of 10ga Belden speaker wire. GRADO SR80e on-ear headphones iMac as music server (2009) Panamax 5510 w/) ISO transformer LG 65" B6 OLED display