You can see the cavities (with black grille cloth) built into the corners of the front cabinetry under the screen in my HT. Neither the depth or height of these enclosures (slightly smaller than a 20" cube) would have accommodated the dimensions of either the PB-3000 or PB-4000. WAF did not support my placing a ported sub elsewhere in the room. The SB-4000 now resides snugly in the right enclosure and the remaining SB-2000 on the left. I'm supremely happy with the quality and quantity of subwoofer output and look forward to many years with the configuration. For purposes of scale, the 16:9 screen is 117" in width (127" diagonally) and the couch (MLP) is approximately 13' from the subwoofer grilles.Hey Mike, Yes I am convinced for pb-3000 and was asking docrog any data points he has for going for sb-4000, and based on his reply it looks like it was mostly due to spatial issues. Thanks!