Just noticed Prophet River has a clearance on Nikon Prostaff 5 to make way for the new line coming in. ~ $530 from $800 for a 3.5-14x50 and and 4.5-18x40 with illuminated reticle. Call Prophet River and ask them their opinion on the quality of the glass for what you're looking for. I've dealt with them in the past and find them to be trustworthy and good to deal with.
FWIW, you can get custom turrets for the Nikon as well and the Nikon online ballistics calculator can print out a dope chart for you to confirm at the range for your specific load. IMO a steal at this price.
http://store.prophetriver.com/liquidation/
I would go with the 3.5-14x50 myself; would serve you very well for a prairie, possible sheep hunting rifle.