I own SEVERAL Nikon Monarchs and Leupold Vari-X IIIs. Both are good scopes, but the Monarchs have better glass than the Vari-X IIIs. Specifically, the resolution and clarity are indeed noticeable, especially in the field.
The only thing that would lean me toward recommending the Leupold in this particular instance over the Monarch is that the Monarch 6.5x-20x has very little eye relief compared to the Leupold in the same magnification range. Keeping in mind that you will be shooting a 7mm Rem. Mag., you might be better off with the Leupold. In this case, you would be spending the extra money to keep from getting a black-eye with the scope.
On the other hand, if you are willing to go down a bit in the power range, you can get a Monarch 3.5x-10x-50mm that has about 3.8" of eye relief.
Then again, if you really want higher magnification, like 4x-16x-50mm, then take a look at the Elite 4200. It has 3.6" of eye relief. I bought one from Jon at the opticzone and put it on my 7mm ULTRA MAG and I just LOVE that scope. Plus, I didn't get hit by the scope (then again, I did install a Sims Recoil Pad which helps reduce the kick).
Zachary
Zachary