I've tried both SS and tube preamps with my X250.5 and I believe I prefer the solid state for the better bass quality. The x250.5 does bass so well that it's a shame to not have a preamp that can do it justice in this department. Depends on your musical preferences however.
And about speaker binding posts on the Pass Labs amps: use spades not banana plugs. Pass amps are not really designed to be used with bananas.
And about speaker binding posts on the Pass Labs amps: use spades not banana plugs. Pass amps are not really designed to be used with bananas.