First off, you don't need 6-20 power for varmints at that distance. A decent 4-12 will work just fine.
But i also understand want...
My choice was a Sightron STAC 4-20X50 with the MOA2 reticle.
Love this scope on everything from 25 yards out to 1,000 yards.
They also make a 3-16X42 STAC, which may sit better, and look better than the 4-20.
I'm going to put their SIH 3-10X42 with MOA reticle on the new to me Forbes 24B in 280 Rem.
Also on my Savage 111 in 7mm Rem Mag.