I have a 7mm STW with a Leupold Vari-X II 4-12 x 40, I went with the higher magnification to help with longer shots. So far I'm really happy with it. I stayed with the Vari-X II instead of the Vari-X III because I've heard the only real advatage was the III gives you a bit more light gathering, say 15 min in the morning and 15 min in the evening. That's a good thing, but I couldn't justify the extra cost.
FWIW I stick with Leupold, I love their Customer Service and their no BS Lifetime warranty. Riflescopes.com has the best price I've found so far.
Hope this helped,