I used to own that exact rig and mine shot lights out with 130 g Nosler partition bullets. However, I always reloaded my own medicine so factory ammo is not my forte.
While desert sheep are not particularly tough to bring down, I do think you should stay with well constructed bullets in case of a poor hit or angle of entry. Many of the big companies now load premium bullets like Barnes TTSX, Nosler Partition or Accubond, etc. Those are my favorites.
You will probably never get another Desert Sheep permit, so I wouldn't worry too much about an extra 10 or 20 bucks for quality bullets. The hard part is your gun will like what it likes and without trying some different brands, you will never know.
Congratulations on the sheep tag. What unit? Best of luck...it will be a blast!