The phono stage is usually the weakest link in the analogue chain. If you've got a reasonably decent cartridge then the answer is "as much as you can afford", because the sound will only be as good as the phono stage regardless of how good a cartridge you have.
Generally you can get more bang for your buck looking at SS phono stages, but IMO the real magic comes from a good tubed phono stage (but they tend to cost more).
Generally you can get more bang for your buck looking at SS phono stages, but IMO the real magic comes from a good tubed phono stage (but they tend to cost more).