i also have usher speakers, the 6381's. the tubes that i find that i like in the belles are the: cbs/hytron 5814wa, rca command 5814a triple mica blackplates, rca 5814 triple mica blackplates, raytheon 12au7 triple mica blackplates, brimar 13d5. i'll go back and put the cleartops in, maybe it's that they are so different in sound from the other tubes that i like. i'm also trying to get a pair of amperex 7316 (at a reasonable price) to try out.