I have the older 801s. My mono-blocs have KT88 tubes instead of the 6550C tubes. The KT88 add about 15 to 20 percent more power. The 8 ohm power is around 285 watts with the KT88s. The 801 were very boomy for 2 weeks while I figured out how to adjust the speakers. The back of the speakers are 3 feet out from the wall and the front of the speakers are 5 feet out from the wall. The speakers have almost 8 feet between them. There is about 4 feet on each side to the wall. I live in an old house with wood floors on peer and beam. There is not a slab of concrete under me.