Hi. I am back...2 years later. I now can say i have compared the Colosseum to the Antileon (in my system). The Colosseum has a far superior, more natural treble and upper mid balance. The Antileon was beautiful, great purity of tone (the inner deep 'ring' of a note)...but ultimately it was dark...clear and detailed but dark. It helped in the overall impression of a rich, organic sound, smooth powerful and effortless. but when i put a Goldmund in (not my taste below mids) but the treble was incredibly pure while also being far more illuminated...i learned something after several weeks of having the Goldmund.)
The Colosseum matches all of the Antileon's natural power, beauty, tonality...but now illuminates the treble and upper mids in a manner that is equally organic as the mids and lower mids all thru the lowest of the low bass...but illuminated and detailed.
I would also say it has shed a few pounds from the Antileon...like a sprinter or a boxer with greater muscles but way more definition too...so that Colosseum takes its immense power and adds dexterity in handling complex musical passages far better. Its just all there in front of you, with multiple complex passages with ease and clarity, no bleeding, no confusion whatsoever...so easy, it makes you wonder why others amps seem to strain so hard to do this. Because it does not seem particularly complex when you hear it on the Colosseum.
Even on the bass, this 'super strong, 5% body fat presentation' means the Colosseum can effortlessly pick up various different lines of low bass in a deep house track 25-45hz and pick each line apart...the Antileon at first seems stronger...until you realize it is 2 notes...when the Colosseum shows you there are actually 5 deep bass notes...and you wonder where they all were before.
Hope that helps.