Hi Hamburger,
Have you heard either? Pls post your impressions if you can. i know the colosseum well, and also the Antileon. unfortunately, have not heard Karan.
I am always curious to listen to other amps (like the new D'Agostino monos). My limited experience in amps includes ARC, Krell, MBL monos, Boulder 2060, ML33H, D'Agostino monos, CJ, (as well as older Aragon, Forte)...Gryphon is my personal favorite after finding it delivers the signal from source/pre with extension and detail, and endless reserves of power. If there is any flavor to Gryphon, it has a natural tonality such that violin strings, etc take on a natural burnished quality in the mids and the requisite pierce in the treble. My fav amp.
Good luck and pls post any impressions!