which $800 used phono to buy?????

I use Acoustech PH-1. Bought it for $600 used. Excellent phono stage, will accomodade LOMC too though not with the lowest output, I guess. Not very versatile in terms of adjustments, but you may not need them. Quality over quantity. I of course use it with upgraded power cord.
I read about Heed but never auditioned it. It is supposed to be very good.
Look at how many PS Audio units are for sale. Yes, they sell a lot of them, I would think, but still it is
suspicious. I wouldn't buy one myself.
Again I am not familiar with it, but you might consider LFD phono as well. They make great electronics.

You'd probably get more suggestions if your title read "which $800 used phono preamp to buy?????".

The Dynavector P75 is very flexible and sounds great to my ears. Very underrated phono stage IMO.

The Whest TWO is a great phono although it might be tough to find at 800 used. I had one and upgraded to its bigger brother P30R but was amazed at how well the TWO did against the next step up at twice the cost.

I demo'd the Fosgate and it couldnt hang with the Whest. To be fair the Fos didnt have much break in time but the difference was so great it had a long way to go.

you can buy a gcph for less than that new. A simaudio lp5.3 is within your price range used.

phono preamp comparison

I think the Linn Linto is fabulous at its used price of about $800. I was truly shocked at how much of a difference upgrading the phono stage made. True, it has no loading options, which will no doubt trouble many people, but it's still worthy of consideration IMO. Personally, I enjoy not having loading options. One less thing to screw around with.

Musical Surroundings Phonomena II.

I have the Musical Surroundings Nova Phonomena. It can run off batteries although I haven't really noticed an improvement in the battery mode. It has a lot of dip switches for gain and resistive loading on the back. Sounds good to me but I haven't heard many in my system to compare.