I have heard the Ayre amplifier it is good, but the Plinius Odeon is a far better match with the Diva's.
The Odeon is really warm and full bodied, quite frankly this is an amazing amplifier, one of my customers has the Diva's with the Anthem and a Cary Cinema Five and that combination also sounds really good. We did a side by side comparison with the Odeon and the Odeon is in another league.
The Bel Canto pre pro is very good sounding but discontinued. I would recommend you get a pre/pro from a company that is planning on a longer lifecycle.
I would go with the Anthem which sounds quite excellent and has incredible support and is upgradable.