Good value phono preamp for MM cartridge

Take a look at the Gram Slee phono stage offerings. They are very reasonable, and have excellent performance for the money.

I use a Lehmann Black Cube with PWX power supply
upgrade, though I'm using it with a low output
MC cartridge (Denon 103D). I've been very pleased
with its performance, and I read an opinion which
said it works even better with MM cartridges. If
you're patient you can probably find one used
for the $400 range.

How about a great value. You can pick up a sumiko or parasound for peanuts and they sound great.

used NAD 1020 preamp used as a standalone phono stage. about $50

Used Aragon 47K for around $300 will serve you well...if you can find one. Plus, it does MC if & when the time comes. You can add a bigger IPS power supply for a bit more umph as an eventual upgrade if you wish. About $600 new, I found it to better my Lehman Black Cube. Very quiet with depth in the soundstage plus good harmonics - the real trick for SS.