ORIGINAL: White-tail-deer
For long range I would definately get at least 4-12 magnification. I would lean more toward the 4.5-14. The 6.5-20 can be a little touchy on the eye reliefat 20 power. Just my experience. I would also consider getting a Bullet Drop Compensation Dial installed. Hope this helps!
http://www.leupold.com/resources/custom_shop/custom_shop.htm
Yep, I second that. I would get a 4.5-14 VX-L with some Leupold rings and mounts.