People are saying burn in doesn't exist, but in my experience it definitely does, whether it be the drivers themselves or my brain from getting used to the sound for a while. Give it some proper listening time and then re-evaluate.

As for amps, I don't subscribe to buying amps for the sound (as you can see, I'm happy with just a Schiit Magni). I think you're probably fine with the amp you have as long as you're able to listen to it distortion-free at the volume that you like. Is there a reason you went for the Diana without auditioning them first? I, personally, can't trust any Abyss products when they're peddling $2k cables and $2k aluminum racks.