Among the solid state phono preamps for about $500 (used), there are the "usual suspects" that have been discussed a number of times here on A-gon. For more info, check the threads listed in the A-gon archives. (To access the search feature for the archives, click on the link "More Chat" at the bottom of the discussion forum threads. On the next page that comes up, look down at the bottom for the search engine.)
I can, from personal experience, recommend the Lehmann Audio Black Cube SE as an excellent choice for a moving magnet phono preamp (the concensus seems to be that it is less desirable for moving coil cartridges). The "SE" version, with the much larger power supply, is a decided improvement over the stock (original) Black Cube, so if your budget will allow, go for the "SE" model. It often sells used here on A-gon for around $500.
I can, from personal experience, recommend the Lehmann Audio Black Cube SE as an excellent choice for a moving magnet phono preamp (the concensus seems to be that it is less desirable for moving coil cartridges). The "SE" version, with the much larger power supply, is a decided improvement over the stock (original) Black Cube, so if your budget will allow, go for the "SE" model. It often sells used here on A-gon for around $500.