It seems to me there may be a much better way of looking at this. You already have a known top-flight cartridge. Why waste time chasing down the few cartridges that might work well with your arm? It seems to me the arm is the weak link. Always improve the weakest link is my approach. For the same money you are looking at spending on maybe the right cartridge you can buy an Origin Live arm that will make not only your Koetsu sing, but anything you put on it.
Origin Live are a breeze to set up. They come with a great interconnect hardwired, eliminating connections and the expense and hassle of matching cables. That's what I did, and my Conqueror is so much better than the Graham it replaced its not even funny- despite the Graham running some very expensive interconnects custom made for me by Ted Denney!! I seriously doubt you will run into any cartridge incompatibility problems with any Origin Live arm.
Origin Live are a breeze to set up. They come with a great interconnect hardwired, eliminating connections and the expense and hassle of matching cables. That's what I did, and my Conqueror is so much better than the Graham it replaced its not even funny- despite the Graham running some very expensive interconnects custom made for me by Ted Denney!! I seriously doubt you will run into any cartridge incompatibility problems with any Origin Live arm.