Ral - My experience is that the Pass amps do not all sound the same (which is true of other manufacturers as well, of course). I believe the X600 to be leaner than the X-150 or X350. Also, please understand when I talk about leaner and warmer, I'm not talking about top-end energy or brightness.
Barrelchief - I owned a Model 10, which some people felt, WITHIN IT'S POWER ENVELOPE, was better than the 12s. In any case, the 302 was/is MUCH better than the 10. They are truly in two different leagues, in my opinion - assuming use in a system of considerable resolution and neutrality.