Schiit Mani vs Atoll P200SE Phono Preamp

I used  that piece of Schiit while my $2500 unit was being  repaired. Great for the money.

Don't waste your time obsessing on what's  "best" at this level. 

Either one will likely be fine. 

Dual monopoly might get confusing, too many pieces on the board...

Dual mono topology, typically a design seen in upper level gear. Think L/R channel circuits independent,  in one box. At this level, considering you're going to plug it into an entry level table, more gimmick than anything. 

The Schiit has plenty of positive reviews, get one for  $150 bucks, plug the table into it and play records, instead of trivial detail(at this level)

Waste of money IMO.

Power supply replaces the wall wart that is supplied with unit.

P3 is a fine table in its price point. Performance expectation should based on your entire system. LPS is the least of your nervosa.