As you can see, by ISO 6400 there's not much you can do about the inherent noise in the photos except change your tradeoffs. But if you're going to use the images scaled down, they still look pretty good.
(Top JPEG, bottom Raw. 1/60 sec, f5, spot meter, AWB, ISO 6400, 18-55mm lens at 18mm. ACR defaults plus Luminance NR 30, Luminance Detail 1, Color NR 35, Color Detail 50)