Krell versus Pass Labs

I have been a a Krell loyal fan for years and years. Recently I upgraded through several speakers to finally settle on the Apogee Diva Ultimate made by Rich Murry in NV. I've also owned the Caliper Ultimate but this new version of the Diva with all ribbon drivers and no transformers is simply amazing. Last weekend I listened to a recently rebuilt version of the Apogee full Range, one step up from mine and these are honestly probably the finest speakers on the planet and I've heard and owned a lot of others over the years, B&W, MBL and so on. One thing about these speakers is that they are completely full range they go past the human hearing on both ends easily. The other thing is that they are incredibly fast and ruthlessly revealing, I mean take no prisoners, it's all here like it or not.

I liked the sound with my Krell Cast system but I have also heard these speaker on other equipment and amps and was amazed how good they can be but my system was not there yet for some reason? Maybe it was just system matching? A friend recently loaned me a Pass X150.5 to try out so I plugged it into my Krell KCT with balanced hook-up. WOW, the high end edginess was gone, the tone quality was much better and more even from top to bottom, the pitch definition is impeccable! Day 2, now with it more warmed up the sound stage opened up a lot and it sounds so incredibly musical! I was stunned how good this little amp is, dynamically it is a champ and does not seem to care how hard you push it, it just sounds effortless regardless of how loud I'm pushing it. A friend who's ears I trust said the 150.5 and the 600.5 are the among the best he has heard with the Apogee's, I didn't think the 150.5 would have enough power but was I wrong. Where have I been why didn't I hear this sooner? I've heard Pass amps before and always liked them but this is in a different class all together than my Krell's.

I think in the end I'm going for the 600.5's and possibly a Audio Research Ref 5 SE? Talk about bang for the buck, the X150.5 is up there in that "cost no object class". Some like the class A amps better for their systems but for the Diva Ultimate I think the X150.5 is amazing. Listening to complex music at a level that is starting to get uncomfortable the meter will swing to about the 3/4 mark with plenty left in reserve, I never heard it compress or strain at all, not even a hint! I can think of several giant expensive amps that could not keep up with this little amp, it's articulation is so precise and effortless. For example to me it can better MBL and Krell mono's and I have been a loyal krell fan for 20+ years!

Rob