Don't think that buying better glass will shrink your groups because if you're getting roughly 1MOA, it probably will not.
Buying a more expensive scope gives you better optical clarity, warranty, and durability (among other things). A $1000 scope won't make your 1MOA rifle into a 1/2 MOA rifle.
Look around and you'll hear funny stories of the thousand ways cheap scopes can crap out on you. It happened to me one time; I actually broke off the vertical cross hair in one of my scopes... you'd think I would learn my lesson.