There is no "very best" commercial preamp as others have already stated. The various offerings mentioned earlier all have their merits no doubt, but they will span a wide spectrum of sound character. If you really want the "very best" you will need to work with a custom builder who can design and build for you a phono stage that has the exact sound you want and the gain you need. This is an area where an experienced DIYer has the advantage over the average consumer who must choose between commercial offerings. In my case, I ended up with a variation of Stephen Robinson's Izzy Wizzy phono circuit (see website below) where I have chosen each part to give just the sound I want. This is a 2-stage tube design with a stepup transformer on the input. Although you can't buy it from your local dealer, a custom builder could build it without any great difficulty and it then can be tweaked to adjust its sound in whatever direction you like.
http://www.izzy-wizzy.com/audio/preampnew.html
BTW, I have no connection to Stephen.
Dave
http://www.izzy-wizzy.com/audio/preampnew.html
BTW, I have no connection to Stephen.
Dave