What is the best phono preamp you have heard?

Nothing can beat the midrange of the BAT VK-P10SE SUPER PACK.
Yes, not even the Aesthetix IO Signiture. I heard them both.

The phono stage in my Supratek Grange is absolutely breathtaking; best I've ever owned/heard in 42 years of audio.

I think it depends very much on combinations. I do not think that, with many years and spending a lot of unnecessary money (of course, within my own financial means) pursuing the so call "best single" component per se, makes me realize that there is one such component exists but eventually to presume that the whole concept is just simply a business ball game. It is strictly a system dependence. You can have the so called "best Phono" but to a larger extent you have to consider the cartridge/s to go along with it. I feel that there isn't any single best PHONO STAGE to cater for different cartridge/arm/turntable/preamp combinations. If so, we will at least not to receive reviews on components. Even reviewers have to admit that their reference system has to be changed from time to time. More so, with careful notice, it is the combination of the whole system that got to be changed from time to time let alone the speakers. You can't simply find any reviewer to just to stick one best component and allow the rest of the system to evolve. So, I would advise that, with these forums, try to find out the musically satisfied combination of components from others and of which, it fits nicely within your financial capability.

Counterpoint SA-9 modified by Michael Elliott:
removing 2 SS buffers, changing to Dynamicaps, removing MC stage, changing output volume control to naked Vishays, changing to high impedence circuit to have tubes directly drive output volume control, better Diodes, changing electrolytics to Blackgates, adding circuit damping

All of these pay off in sound quality.

I have`nt heard them all.The Herron is superb,and so is the Aesthetix.I listened to the Manley for a week when it first became available,i was impressed,but not blown away.I sold my first Walker reference while i was doing all this listening,regretted it,bought another,and now i am a happy camper again.I am a tube freak too,but there is something about this Walker phonostage that is very satisfying.Now mind you,i did say i have`nt heard them all.