Best sounding transistors

Many people talk of tube rolling and the sonic differences they impart.  Output transistor are not easily rollable since they are soldered in place, but I'm curious about the sonic signatures different transistors might have.  Who makes the "best" ones?  Which amplifiers use them and what is the native/optimal output impedance on these devices?  I know there is a lot more to an amplifier than just the output transistors, but I'm just curious about this one aspect.  I'm not an electrical engineer either, so please keep it simple.  What do the Pass amps use?