Best Preamp for Ayon Orthos II monoblocks?

Since you are a tube man the obvious choices are Audio Research and CJ; I don't see how you could go wrong with either.

Someone I knew had the CD-5 and an Ayon integrated amp; the pre amp section was not good in either and my 20 year old Meridian 200 transport and Audio Synthesis DAX sounded better than the CD-5. He still has the Ayon amp but has sold the CD-5; he now uses a Conrad Johnson LS 17 with the Ayon amp.