Well, I guess it *could* depend on the vintage and overall power output of your receiver. While Denon is a highly respected brand and any of their modern components should be fine, if you are listening at very loud volumes to a very old, 30WPC unit, you might benefit from upgraded electronics.
Wid's suggestion is a good one. You could also prevail upon some local retailer to take your M50's in to the store and audition them against other speakers using his equipment.
How old is your CD player? While I seriously doubt there would be an audible difference, DACs have improved somewhat over the last 20 years.
Of course, it is possible that you would simply prefer some other speaker's character. I like Jay's analysis.
