If your gonna spend that sort of money you really should demo, also there will be very few if any places that will sell them over the internet so you might as well demo if your going to a store to buy it.
I had this same challenge prior to buying my A1XV a fwe weeks back.
First of all like people have said you really need to listen to both options, if not for any other reason than we are all different and regardless of what other people and reviews say YOU might not like the sound !
I demo'd both of these set-ups and the Denon was a no brainer for me, it is not only fantastic for both music and movies but it is so flexible.
The Arcam was great but was not as strong in the Home Cinema sound (by a noticable stretch). Depending on what your main use will be this might affect your choice. Having said that and as a long term Arcam fan the Denon IS very impressive in HiFi mode with pure and direct sound options.