This subject is highly debated. Check forums. Both configurations can work well. Set-up is key either way. What works well in one room may not work well in another. If you have two subs then start experimenting. Try one sub to start. between speakers, near front wall, side wall, offset, centered, equidistant from listening position. Switch it out with the second sub once you find some spots you like. Next, stack them in the center, try stereo (one by each speaker). Try one up front and one off to the side wall.
