I would seriously consider making DIY bass absorbers for the corners as opposed to the foam ones. From past experience, IMO, there is NO comparison between solid or even straddled 4-6" thick fiberglass, mineral wool, cotton and ANY foam in terms of bass absorbers. This applies not only to performance but also to cost. I'll guarantee you that you can do some nice fiberglass or mineral wool absorbers covered with cloth to match the wall panels MUCH cheaper than you will get any decent (being nice here) foam product.
If you have limited space in the vertical corners, consider the horizontal ones (wall/ceiling intersection). If aesthetics are rearing their ugly head, consider building a false soffit that will look nice but act as a huge broadband bass absorber.