Dave, youre right, your system is a tad bright, meaning it lacks harmonic complexity in the upper octaves and spatial liquidity - something you definetly want with the music you listen to. System building is a careful balancing, but you dont want to swing too much either way with any given component or its hard to fix, ie using the Cardas to mellow out the lack of harmonic purity in the Krells/Naim. Here's some ideas. The Accuphase is a good idea and it has resale legs, if you can find one. I haven't heard the Gryphon Callisto, and I'm sure its nice, but since Skull at $tereophile banged the amp, its a harder resale on the whole line in the US. Irrelevant on sound, but realities are realities. Here are two systems:
A)
Sony XA7ES CD player: your micomega is a weak link. Sell it. Sony is great transport ($1000). Built like a tank.
Keep the Levinson DAC
Accuphase Integrated
NBS King Serpent II intercon ($425)or Purist Proteus Rev B ($400) or Cardas Nuetral for less $ ($250)
Get rid of the Naim: cheap, good pacing, but spatially challenged (and that is what youre getting with the Accuphase), so...Purist Colossus Rev B 8ft, biwire not much more ($750) or, if you want to stay Cardas & biwire (cant remember if AE's biwire) then Cardas Nuetral biwire 8ft ($700).
Keep the AE's, they're nice, but, as youve found out, dont tolerate thinness upstream.
B)Consider an EAR integrated w/ EL 34 output tubes (substitute Electro Harmonix) & go NOS on the inputs instead of Accuphase ($2500)
Get a Bybee Sig conditioner ($600) & experiment with dig cables (Marigo, Illuminati etc.)although Aural may be good here. Custom Power Cord Co. #11's everywhere ($150 ea.)
I know it sounds like a gut job, but not really in the long term. Incidentally, the Krells are a down step from either of these systems, and by a wide margin. Good Luck.