Krell KAV400 VS Musical Fidelity A300 A 3.2 A3.5

The difference is clear if you listen to them. Both have their adherents. I would highly recommend listening to both to see which sound you like. Krell - forward, detailed, unforgiving. You'd better have a good source because the Krell will let you know every flaw. MF - warmer sounding but not exactly the tube warmth but it seems they're designed to have some sort of "presence." Rounder, somewhat fuller. The highs can be just as etchy as the Krell but are somewhat covered by the fuller lower end.
If you have a great, and I mean really good, digital source and don't listen to a lot of boosted, compressed music then I'd go with the Krell. Otherwise if you want something more forgiving the MF.

To each his own. I spent a lot of time and money on "revealing", "nuanced", "accurate", "detailed", and the coda: a quote from The Matrix: "You know, I know this steak doesn't exist. I know that when I put it in my mouth, the Matrix is telling my brain that it is juicy and delicious. After nine years, you know what I realize? [Takes a bite of steak] Ignorance is bliss." I concluded I like what sounded good over what really was 8 days a week.