sorry but i have to give you my 5 cents. look closely at the lexicon mc-8 or mc-12.
I would rate them basically the same way you have them written. Arcam first, Krell a very close second, and the Aragon 10th or 11th (i.e., not anywhere close to being in the same league as the other two). The Arcam and Krell both provide excellent Home Theater playback in Dolby Digital (might give a slight edge to the Krell). For music, the Arcam is a little more clean sounding while the Krell has a more "tubey" sound to it. The Krell sounds very similar to a Conrad Johnson pre-amp to me.
I have personally owned the Aragon and would not recommend it. Dolby Digital is nowhere near as clear as the other two and 2 channel/multi-channel analog passthrough is cloudy with a slight bass emphasis.
Hope that helps.
I have to disagree with Sedona_sky_sound. I have owned ARCAM NAD ROTEL ANTHEM and ARAGON processors. In terms of sound quality there is not doubt in my mind that the Aragon stage one is superior to most of the competition especially for two channel playback. Its definitely a reference component in every way and after spending months with seven processors I have come to the conclusion that the stage one given the heavily discounted prices is the way to go.
I've never had the Arcam or Krell in my system. I have owned many prepros including Lexicon, Citation, Parasound, Outlaw, Sherwood and a couple of tube/solid-state preamps. Among the prepros, the Aragon Soundstage (~1100 used) and Aragon Stage One (~2k used) are the best performers for movies and 2 channel music (besting some 2 channel preamps), as they are both based on Aragon's top of the line Aurum preamp. At the current discounted pricing, these two prepros are great buys!