@nightfall and others -- sorry FOUR 6SN7 tubes rather than SIX. My bad.
I still prefer having a preamp with one. Why? Cost: they range in price but maybe $30 bucks and up (times four). I'd rather spend money on having a variety of 6SN7 tubes to try different sounds with. I don't want to buy multiple quads. IMHO, having amps with that many tubes is what would push me toward a solid state preamp.
Sure thing about the QS. I upgraded the caps in my preamp and still didn’t wind up keeping it.