P3RS, P6, Marantz TT or RP8

I know that the Rega guys have that "we don't need to adjust it" approach and that's fine and, of course, their tables and tonearms are well regarded...still, since pretty much everybody else allows adjustment with no negative issues when designed properly, I'll simply stick with one of those.

I would wait out for a used Dr. Feichert Volare and skip all the Regas and Marantz. 
Not familiar with Clearaudio Champ 2. 
Another option is VPI. I own Prime X and like it a lot. 
TMR has a used one here https://tmraudio.com/products/vpi-prime-x-belt-drive-turntable-no-cartridge

Has a VTA adjustment tower which helps make precise VTA adjustments. Yes the unipivot tonearm can be a pain with VTF and Azimuth but once dialed in, sounds amazing. 
 

The new Pro-Ject Debut Reference 10 has a lot to recommend it. All tonearm adjustments are made via set screws…including azimuth and VTA.  The 10” arm has superior bearings and comes with a mass appropriate cartridge made for them by Ortofon, based on a 2M Red. Its design feature is discrete L/R coil pins with no shared ground, allowing “balanced” connection…like all MC carts. $1499.00 so in the same category. 

I'm not familiar with the Marantz 'tables, but you certainly can't go wrong with any of the Regas you mentioned at their respective price points. 

I toyed with all of the Rega turntables you're considering but - in the end - I went with a Michell Audio TecnoDec and T8 tonearm (the T8 is essentially a Rega RB880, with maybe a few tweaks by Michell).  The Michell inverted bearing design was really what sealed the deal for me - it's the same bearing used in the most expensive Michell models and is unique in its use of an Archimedean spiral milled into the spindle that helps to continuously circulate bearing oil.  It's certainly one of the quietest 'tables I've ever heard and I have to believe the bearing design is a big part of that. 

You can use a wide variety of arms with the 'table, including the usual suspects from Rega and Michell (whose arms are modified Regas), but Michell can also supply armboards for a wide variety of arms.

Just a suggestion if it's not something you've considered.

I was looking for a used technodec but they are almost non existent.