Re: optic question-new to this
It's your money.
The SPS tactical shoots better and is cheaper.
http://www.snipercentral.com/vtr.htm
Good luck and I hope you get a good one, we would like a range report.
As far as your scope selection goes, the Nikon will have very good glass, but 50 MOA is not a whole lot. That is 25 up and 25 down from center, a 20 MOA base will give you 45 up and 5 down from center which is squeezing it a bit. When you get out to 1000, you'll be at the top of the adjustment range, looking through the glass near the edge, usually not conducive to a clear picture.
Just a note, my Falcon Menace is advertised to have 90 MOA, is in the same ball park price wise (about 400 after taxes)and is mil/mil vice mil/moa.
Not saying your choice is bad, Nikon makes a very fine scope with very good glass, but if you truly want to get way out there, you might want to consider a scope with more adjustment.