The rangefinder makes that list an impossibility
The only choice you have is the Nikon and it is not combat oriented. And the rangefinder sucks. They are hit or miss when you have a good one, let alone when you have one that is integrated in an all-in-one setup.
Go to Scheels or Cabelas, they usually have them in stock–pull it out and rangefind off of various areas in the store. Also make sure to go back and re-range things you already ranged a few times. There is a great deal of fluctuation in the readings.
You don’t need a laser rangefinder to range. You’d be better off learning to range off of your reticle. There are many different choices in this department, just check out the reticle specs before you buy.
If you want to make ballistic calculation easier, the KAC software for the ipod or a Barrett BORS would work out well but is probably outside what your looking to spend.
You can also get a BDC reticle that will somewhat match the ballistic profile for your bullets/caliber but these are by no means fool proof.
And the bottom line here is you are not going to get a $600 scope that meets your combat requirement. The closest/cheapest thing out there matching up to a .308 would be a IOR M2 but its not variable power.
By defining the variable power and combat use, your automatically looking at 1200-1600 to start and thats a minimum range for a quality optic.
Night vision capable is also a subjective term. Are you talking about looking through the scope with goggles or mounting an optic with a nightvision scope on the rifle? Almost anything is “night vision capable”, but whether or not its designed to work in tandem is another story. Using goggles to try and look through a scope just doesn’t work very well, unless its a quick acquisition cqb optic like an Eotech or Aimpoint.
Again, your looking at at $1200-1600 scope, probably $200 for a mount and then whatever your night vision setup is going to cost you. Anything Gen 2+ is going to be $2000+
Nothing out there meets your 600m requirement.
http://www.bhphotovideo.com/c/product/498322-REG/US_NightVision_000411_UNS_PVS_22_Universal_Night_Sight.html
http://www.bhphotovideo.com/c/product/438597-REG/ATN_33010_Elcan_SpecterIR_2X_Thermal.html
This ulitmately goes back to your requirement being somewhat sketchy.
You need to determine what it is your trying to do, realistically.
What you’ve defined sounds like “mall sniper”.
Almost any nightvision requirement is going to put you well inside 300m of your target.