It really depends on what type of motion graphics you are trying to render. I would question whether you need the full 576 samples to achieve the renders you want.
Decrease AA Samples - If you switch to Branched Path Tracing, keeping square samples on, I would try reducing the effective AA samples to 20 or under (try 4 or 5 in square sample mode). You can increase the other sample rates to get multiples that equal 576 (although you may not need it for Transmission, Volume or Subsurface, depends on your scene). Decreasing the AA samples will speed up background tile rendering significantly. As long as you have enough AA quality for the edges of your rendered objects, you should be fine.
Turn Off Sample All Indirect Lights - Also I'd turn off "Sample All Indirect Lights" if it doesn't affect your scene quality noticeably. It will make quite a difference.
Optimize Tile Size - Small tile sizes (16-32 for CPU) seem to be more efficient around the edges of objects where there is a transition area between object and background. However, once the tiles are rendering 100% background it seems a little larger tile size (64-128) is more efficient in Cycles. You need to find the optimum balance between the 2 sizes depending on how much background is being rendered in the frame.
If these suggestions do not help, perhaps you could share a sample frame render so we can see the type of scenes you are trying to render.