First, your avr has a bass management system. This is will help setup your system for the best performance. Using a Y adaptor on the sub may increase your sub output by 3-6 db. Most new movies are master correctly. Pioneer recommends setting the LFE to 0. If the bass is to much, then you can set it to -5 or -10 for example. Usually with one sub and using your avr, set the phase to 0. The avr will match the sub and speaker phase for you. The sub xo should be turned all the way up. This is to allow the .1 or LFE's to be fully appreciated. The .1 channel is a production channel for the movie makers and has info from 120 Hz down. The subwoofer is a playback channel: therefor setting it to less than 120 Hz will omit some of the LFE's.
Klipsch RF 7 based HT 7.4, Pioneer SC 35, Acurus 200 Five, Dayton 18 Ultimxa Dual Sub Cab(2), Dayton 18 Ultimax Large Vented Sub Cab (2), on Berhinger I Nuke DPS amps, Samsung BDP F 7500, Asus/My Book Live HPC 4 TB
Yaquin VK 2100 amp, McIntosh XR 5 speakers, Samsung BDP F 7500