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

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.

Musical Surroundings Phonomena II.

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.

phono preamp comparison

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

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.

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

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