I used to have a technics receiver, basically the same as what you have. Set it at 100 and what ever speakers you set as small they will not reproduce below 100. Even though you have mains with dual 6.5 inch woofers I personally would set all speakers to small, filter at 100 and on your sub turn the crossover dial to its highest setting that way you get the sub crossover out of the way. The power supply on that receiver is not that big so I would not set your mains as large, it will perform better set at small.