To me, it was easy. I tried the Denon 1913, 2313, and the 3313 on my system. The HK2600 that I now own produces a much clearer dynamic sound than the Denon. If you are looking for the number of connections, etc, go with the Denon. I recommend Harman Kardon for sound. This is my personal preference. If possible listen to them side by side, and preferably in your home.
Main. Marantz SR7008, UD5007, Integra CD3.2 Paradigm Reference Studio 60v5 fronts, Reference Center, Rears, Def Tech Super Cube