The four brands you mention are all very fine and among them you will hear
some of the best available, do you really want to muddy the waters with another
12 brands that will be mentioned? You are already on the right track with the
four you have identified, they are all first-rate and listening is the only way to
make your pick - of the four, Pass was my favorite, but that was the Class A
series - Aleph, XA.5. SIM, Ayre, Pass, Classe --- I don't think any of these can
be considered "dark", if you don't find an amp you like from these, you might
want to consider tubes.
By the way, the amp you have is already pretty darn good - a McCormack
upgrade might not be a bad idea at all.
some of the best available, do you really want to muddy the waters with another
12 brands that will be mentioned? You are already on the right track with the
four you have identified, they are all first-rate and listening is the only way to
make your pick - of the four, Pass was my favorite, but that was the Class A
series - Aleph, XA.5. SIM, Ayre, Pass, Classe --- I don't think any of these can
be considered "dark", if you don't find an amp you like from these, you might
want to consider tubes.
By the way, the amp you have is already pretty darn good - a McCormack
upgrade might not be a bad idea at all.