How much to spend on phono preamp

I am a fan (owner) of the PS Audio NuWave Phono Preamp. ( $999 )  The sound is exquisite and can easily handle MM/MC . Check out the specs at the PS Audio site.  I also like the ability of ripping ( DSD/PCM ) my vinyl direct to my computer/music server to preserve my collectible vinyl. 

as little as you can or as much as you have to!

+1 for anything Herron. I also suggest Lounge, Sutherland, or the JC3+

I bought a used Manley Chinook from a dealer and am very pleased with it. It is extremely flexible and you can roll tubes for a highly customized sound. I have used both MM and MC inputs. I have no desire to buy another. That does not mean that I won’t one day! LOL