Hi I don't think the SE upgrade is officially available as yet at least not in the states. If I remember correctly the tube becomes specially selected NOS 5670's utilizing special sockets with compatibility circuits in-built as well as noise filtering in-built.
The volume control in the DP777 is one of the best kept secrets out there period. I sold both my MFA Reference Pre's (the Reference and the Baby Reference) which I owned simultaneously once the iTube came along.., I will explain. The MFA Ref TVC's were flat out the finest volume control units I had heard and that includes the ARC 40th Anniversary 2 Chassis Pre, Concert Fidelity (USD $24K), and they (MFA units) flat smoked the Allnic L/H 3000 (the one with the bigger mk2 transformers), made the allnic literally sound flat out wrong/ just wrong is all I can say.
Having said all that I disagreed with the Stereophile review of the Baby Ref in one point and one point only; both the ref and the baby ref have a signature (in contrast to the reviewers stance) and as someone who owned them both I knew it well. It was a beautiful fullness which was delivered to the sound, not a coloration but literally a corporeal body to go along with the musical event. That is why I bought the baby ref (for the second system). Unlike the reviewer in Stereophile, I do NOT agree that they are perfectly transparent (not sure those were his exact words) and the DP777 as well as Pure Musics 64 bit volume control illustrated that quite easily to my ears. There is a very slight micro shading of low level detail/information with the TVC's that the AMR laid bare. Specifically things like a singers breath and or inflection when singing.
The trade-off was the body :) So, the delimma, detail or body? I chose body hence the 2 MFA units. Then came along the iFi iTube and it did EVERYTHING the MFA units did PLUS it was as transparent with the AMR as the AMR alone. So I sold both MFA units and now I use the DP777 volume control into the iTube set at 0dB gain and in buffer mode with 3D on and it is phenomenal.
In case you didn't know.., the guy (Thorsten Loesche) who deigned the Reference transformers for MFA is also the man behind AMR/iFi :) So he was able to electronically bring the benefits of the transformers with complete transparency to the iFi line. Caveat.., the iFi is NOT transparent if you engage the 6dB mode. If your' system is lean or sterile, the +6dB may work for you.
All that to say that if you add the iTube to the AMR you may find that is all you will ever need. I have not looked for a pre since as I have heard NONE that can beat that combination and I have listened to a great many very very expensive preamps. Hope my 2 cents worth can be of some help :)
