Agree, IMI is almost as good as Black Hills and a decent value for the price.
Your rig will do fine with respect to short line loads to the point where you would be surprised at what it can use and shoot a clean score at 300.
The AR Service Rifle isn't easy on brass. Your IMI brass is good, but don't expect long life out of the brass.
I will suggest you run your 600 brass separately from your 200/300, but there are folks who run it all together and do well.