I'm just waiting to hear back from Tommy O'Brien (owner/designer of Digital Amplifier Company) concerning the input impedance. I wonder if the LDR preamp will sound really good with the Cherry Ultra, since the amp is so clear, precise, and full (yet not harsh). Its the best amp I've ever had, sound-wise. I wouldn't want to make it unlistenable, but I don't believe that would be the case. It is nice to be able to do a lot more low level listening and having it sound so good and detailed. I used to have to really turn up the volume to be able to hear details, but not with this new amp. Even at high volumes it still sounds very good and listenable.
The Ultra has balanced inputs, but I have adapters on it to hook up to my unbalanced preamp. I was looking at a balanced AR LS2B Mk II preamp, but if I can avoid it I'd rather go passive. I may go and build a balanced kit pre with both balanced and unbalanced inputs since all of my inputs at this time are not balanced. 'Or', maybe I should just build an unbalanced one to try out your preamp. I wish I'd caught your sale, but I'm about a month too late.
One way or another, I will get your product and try it out. I'm looking forward to hearing even better sound out of my system.
BTW, the Infinity RS 2.5s are supposed to have around an 87db SPL, not 83db.