best phono preamp under 500?

Graham slee products
Bellari VP129
music fidelity

get to high 6's and get the PS Audio GCPH.
Then you have an upgrade path with Underwood to
truly compete with 10K phono preamps and out of the box
it stands up to anything under 2500 that I've heard.
There's no such thing as "best" but I would definitely check out the new Musical Fidelity V-LPS II that is just going out to dealers in the US. It retails for under $200.
Lehmann black cube is worth a look. No longer <$500 new, but used examples should be well under that price.