I'm quite happy with my SLX m675 brakes, but looking at their price, I might but some m520 4 pot calipers to try. They come with olive fitting, I've never heard of it myself, but is it possible to change them for banjos?
There are curved banjos, but my doubt anyway, is if it's even possible to do it due to threads having different size and location inside the caliper, or whatever.