Classe CA 400, Pass Labs X250 and X350 comparison.

I am thinking of upgrading my amplifier. I have a Bryston 4B-ST. My system consists of a Classe model 6R preamp, Coincident Total Eclipse speakers, Theta Miles balanced cd player along with a Arcam CD92 cd player. I am leaning toward Pass Labs X250 or X350 (more power). Along with a cheaper alternative the Classe CA 400. I like blues and classic rock for music choices. I am looking to improve dynamics,detail,wider/deeper soundstage and maybe improve mids and highs. I would greatly appreciate any comments, opinions and suggestions regarding these amplifiers. Offering suggestions about how any of these amps could improve over my Bryston are important. I think Bryston has a good reputation for having good bass, would the amps I have suggested improve that? Thank you in advance, Somebody please respond. One other note the Pass Labs amps have the X250.5 model is it a notable choice over the other two. There is quite a considerable price increase to purchase one?