Has anybody ever stacked 2 HPR 181i subs? I have 2- 152i's, 2- 181i's and am in the process of purchasing 2- 153i's and 2 more 181i's. From what I've seen, having the 153i on top of one 181i sub isn't quite as high as i would like, so I was wondering about stacking the 181i subs. I know the mouth is at the bottom of the sub though, so would this work if i laid the cabinets on the side and stacked? Just wondering if anyone has done this. I can always build a platform and keep the subs side by side on the ground, just wondering if this way would work too.