I am looking at getting some new glass for my 300 RUM. Currently its topped with a vortex viper 6.5-20x44mm (this will be moving to the 22-250 ). I am mostly looking at the Viper HS-T either 4-16x50 or 6-24x50. But I am wondering if I will be getting any better quality of glass if I don't upgrade out of the Viper line??? My buddy has the viper HS and it seems a bit clearer than mine, not sure though. Another guy told me that at longer ranges or low light conditions a lot of these other scopes would perform much better. I plan on shooting the gun out to 700 yards and eventually work out to 1000-1200 yards maybe longer.

I'm also considering these:
Zeiss Conquest
Zeiss Conquest HD5
Leupold VX-6
Leupold Mark 4

What I want is exposed turrets with zero stop, and a scope that will hold zero with the recoil of the rifle and have quality turrets.

Because I know a guy with connections, I can get discounts on many of these scopes, but by the looks of things I would be saving atleast $250-$300 by going with the HS-T (compared to the cheapest scope above). Which might help with the custom work on the gun I will be having done later this spring. So are any of these other scopes actually worth the extra money? Or should I just save the money for another year or two until I can put a Nightforce, Huskemaw, or Swarovski on top of it after all the custom work is finished?