Preamp for my CODA 5.5 amp

I'm using a SimAudio 740P preamp with my 5.5, and they make a great pair!  My favorite amp up to this point with the 740 was the Pass X250.8, and I think this pairing is just as good overall if not better.   I don't personally see it as a hard requirement for a lush or tube preamp to pair with the 5.5, not that a resolving tube preamp wouldn't also be a great match.   I don't find the 5.5 forward or fatiguing at all, and that is after owning the warmish XA30.8 and the very easy on the ears AtmaSphere Class D monos.   Personally, I think it would be a disservice to add a preamp that masks resolution and detail with the 5.5 as its so clean and resolving with an incredibly refined high end.   Why hide it? :)

FWIW, this most likely won't be of any help but I am using the Legacy Audio Wavelet II into my Coda S5.5 which is driving the mid/treble of my Legacy Focus XD's. The Waveet is also an external crossover and has Room Correction DSP specifically programmed for the speakers I have. The Coda amps pair exceptionally well with the Legacy speakers. 

 My Backert Labs Rumba tube hybrid preamp has great synergy with the S5.5, adding in some beautiful tube harmonics combined with hi resolution. 

Like @yyzsantabarbara I was using a Holo Audio Serene KTE on my Coda #8 with good results. Very transparent sounding. I now have a Balanced Audio Technology (BAT) VK-80 Tube preamp that I am extremely happy with. Sold my Serene preamp.

You’d get much better and more targeted recommendations if you share what specific improvements you’re looking for and what sound characteristics in general are most important to you.  Do you find the Coda to be sufficient to drive your Aerials?