@lak - Allnic equipment is some of the best available in my opinion. Your Allnic integrated, as you indicate, should drive the Double Impact with no problem. I've always been impressed with Montana speakers but have never heard the EPX. For me, the real breakthrough with these new Tekton speakers is the tweeter array. It presents the upper midrange and treble in a completely natural way.
This is obviously just conjecture on my part, but the only area you may feel is not a clear step forward is in the bass. The bass produced by every Montana speaker I've heard has been truly excellent. I'm not saying the Double Impact's bass won't be very good just that might be an area it will, at least, be a "wash" between the speakers. You may want to wait for the Mini-Ulfs to come out or even spring for the full Ulfberthts - simply based on what I remember hearing from Montana speakers generally.