Perhaps not. I forgot you probably have a limited choice of x-over frequencies on the surround processor, so the beta might not go low enough. You might get away with 80Hz but you would want a high order slope when running a Beta that low. I quess 75Hz 2nd order is standard. It's just my poor stereo brain in a big surround world.I know the 1Pi (Alpha 8) is great. I helped a friend build some 1Pi kits and he uses them for main, center and rear with a retail sub, very nice indeed. I was very impressed and will recommend to anyone looking at this size and power class of speaker. It is interresting that he did not have issue with the magnet under his TV, but I can not say if yours will be the same. All considered, My first thought the other day was 1Pi and That is still what I think. Wayne has everything you need, and probably has a good idea how to pad down the apt 50 to work in a 1Pi, since I know you want a horn on top.
Thomas