I think you will be better off running the dedicated line off the main panel. But if you are running out of room and need a sub-panel, make sure the ground of the sub-panel is connected back to the main panel. Never connect the ground from the sub-panel to a separate ground rod otherwise, it will be a safety code violation and may introduce unsolvable ground loop problem.
Adding second "dedicated" breaker box.
I am getting ready to hook up 3 20amp dedicated lines for my system and am wondering if installing a second breaker box directly off of the main line would be worth the effort. I thought this would be a better set-up than running them off the main box or a sub-panel. Thanks for the replies in advance.