Best Amp for Revel Ultima Salon 2's?

Hi All - I've been enjoying my Revel Ultima 2's, but feel it is time to upgrade my amps (Emotiva XPA-1's). I am using a new Classe' CP-800 preamp, but I'm open to suggestions on a new amp/preamp combo from fellow Revel Ultima Salon2 owners.

I would love to go to all tube gear, but feel the speakers are not the most efficient and may require SS or Digital.....but I could be wrong.

Thanks in advance.

Mike