I'm using the X-600 monoblocks on my 1 ohm speakers. I have a large room, and I like it loud at times. I cannot imagine better monos. I have run all tubes, and have had no trouble switching to Pass X amps, and pre amps. They are perfectly invisable partners to my tubed CDP and speakers. I still must have tubes somewhere, though. With a 4 ohm load, the 600s may be overkill. They will be running class A all the time.... That's good.
Of course, for the price you are looking at, you will need to buy the 600s used. That is no problem, because Pass amp reliability is legendary.
Of course, for the price you are looking at, you will need to buy the 600s used. That is no problem, because Pass amp reliability is legendary.