I am not sure why you are mixing the brands if you plan to upgrade both. Why wouldn't you stick with e.g. Parasound? Or Bryston. Etc.
You will likely not struck out with 2 different "random" brands for a pre and power amp to find a perfect match. I would pick one component to upgrade to make the jump and try a number of models. Then I would upgrade the other components. Patience is your best friend :)