Lots will work. I like the RCA RCRP05B (<$20 at Best Buy, Walgreens, Sears, etc. and online). It's made by the same company (UEI) that makes the DirecTV remotes, but has quite a bit more flexibility. For example, you can add functions for your Denon receiver, like discrete input commands which may not be in the OEM remote.

The Sony RM-VLZ620 is another good choice.
The main things you're looking for here are volume punch through and macros.