An excellent tube circuit design would yield the liveliness, sound stage, layering, and ambient decaying that many ss designs still come short of. In contrast, an excellent ss design has bass extension, impact, dynamic, and transient attacks that many tube can't quite match. That's why I have been preferring the ss amp and tube pre combo. The ss amp design gives me the luxury of having it turned on 24x7 and not worrying inability to drive difficult-load speakers. Because of TRL extreme low noise-floor, grain-free nature, it makes matching higher sensitive speakers possible also (heard ST-225 with 90+ db speakers before). The tube rolling at pre gives me that flexibility of adding a touch of warmth and improve liveliness without sacrificing (much) neutrality and full spectrum balance. I have no complaint but prasie for my TRL monos. The high gain amp design makes finding a matching pre a bit tougher. However, that's the inconvenience I am willing to go through considering the musical fulfillment the amps have brought for thus far. :)