It sounds to me like you MIGHT be able to rearrange and consolidate things and be able to fit another circuit somewhere for the DC.
If it was mine, I'd probably sit down and make a good diagram of all the panels, breakers, and exactly what is connected to what. While at it, I might double check the breaker requirements for the large components to make sure they don't have larger breakers than required, regardless of the wire size. I also like to hook a clamp-on amp meter around the hot line in the box (not a good idea unless comfortable working in a hot breaker box) and write down what each large device is actually pulling at full load. Just for information.
With this map in hand, an electrician could more easily double-check and review your entire wiring installation and give advise on easily done options.
JKJ