What are you after? That Aleph 5 is a pure Class A with output of 60 watts per channel (8 ohms). The Aragon 8008 BB has a bias of 26 watts into Class A (which is pretty high for a typical Class A/AB amp). However, the Aragon is going to be able to push more current and bass power overall, due to bigger power supply, etc.
I have heard the Aragon. It is a nice amp, but it is voice VERY warm. I don't really know what the Aleph sounds like, but based on
Is the Aleph 5 running out of gas on your speakers? Or are you looking for something that supposedly has better sound quality?
The Krell FPB amps are likely to have much more resolution, attack and detail than the Aragon. However, that Krell Class A is going to be a very "creamy" sounding Class A, especially in the mids with piano and voices.
I think the Pass Labs XA series is not going to be "creamy" like the Krell, but I think it may still have an element of warm sounding sonic signature. It may have more resolution than Aragon (which is VERY warm sounding).