Favorite phono stage in the $500-$800 range?

Definitely the Ray Samuels F-117 Nighthawk battery powered unit. It's tiny but it sounds amazingly good. The battery will run for around 48 hours of playtime before recharging is needed (when new). I love the sound of this unit and for the money I know of no other that can touch it.

I just had my battery replaced after about 4 years of use and it sounds like new again!

Plus all the controls for gain and loading are on rotary knobs right on the front panel. So setting it up and dialing it in couldn't be easier. I uesd to own the Musical Surroundings Nova Phonomena but to my ears the Nighthawk sounds better and the lithium ion battery lasts way longer.

Dynavector P-75. It's an excellent value, and low output cartridges are no problem at all. You won't have to worry about upgrading in the future.

Lehmann Blackcube SE

The Jolida JD9 mk ii is right in your price range. This is a tube-buffered phono stage with a great amount of configurability, with separate gain settings for LOMC, HOMC, and MM/MI. It also has a wide range of resistance settings for MC and capacitance settings for MM carts.

There are also some fairly inexpensive tweaks that are drop-in replacements--higher quality 12AX7/5751 tubes and better op-amps--that elevate the performance for low money and no soldering.

I used mine for 3-1/2 years and it's been really good. I only replaced it when I encountered a rare opportunity to get a MAGI Phonomena, which has been compared favorably to the Manley Steelhead.

Check out the Graham Engineering phono stages. I don't know what your cartridge MM vs MC, they make different amps for each. The price is right and I really like their sound. If you have an MM, HOMC,-Mid output cart, the Graham Amp 2 SE is killer good for about $400 new.