I found with my SP-5000s they were soft and mushy with my SS 85w pushing them. They're rated @ 90w, 102db, now with two MC275 MkVI mono bridged @ 180w tube power. Well lets just say they love it, they have long legs over the stated wattage. Much more responsive clear hard hitting bass with optimum tube power driving them. I did run them with one MC275 @ 90 WPC at first and they sounded very good but it was very easy to just bring the volume all the way up. I knew then I wanted to mono the 275 and the sp-5000 will handel it.