Accastil , I hope you saw my 2nd addition on page 5 the very long list of replies to your question in "General Audio" - about a CD player before an additional Amplifier .
From the nature of your amp question here I really think some-one has been giving you bad advice and you will simply end up spending a lot of money and gettting no "better" but only "louder" , and , if you buy "behringer" you may get "worse" quality with the louder . Behringer is a low price semi-pro / home recording / small PA products manufacturer - it is not quality sound - your Marantz is much better !
I have spent years working with Pro and Semi-pro Audio and Recording . "Crown" were good for amps and hopefully they still are , but this is not the audio area you should be looking in unless you know a lot about what you are doing as there are numerous things to take into account and I am not going to even start writing about those . Stay with home audio brands and things will be compatible , seriously , Chris .