Look into refurb 600, 650 or 700 to save money. I have a couple of refurb 600's I got for around $30 that work fine for a 5 device system. It that's still too much, many cheaper universals will also handle all functions of all your devices but will be more difficult to operate since the button names may not match the functions. For example, your Denon probably has around 400 functions (about 50 of which are on the original Denon remote). On harmony, you may have to put Zone2 Center Level+ on the 100th page of the screen, which will take you 50 button presses, at least, to access that function. Anything over 5 or 6 pages is impractical in my opinion. On a universal with no LCD, you may have to put such a function on double-shift-6, for example. In that case you'd either want to back off on your "every function" requirement, or make some cheat sheets listing the functions and buttons.
I find it's best to relax the every function requirement a little. I realize that I'm not going to use most of my receiver's 400 functions every day, so I put the ones I use often on the remote and am ok with pulling out my original remote for the others. So relegate your universal to every day functionality and use the original remotes for things you might only do a few times a year. Otherwise, you'll be endlessly paging through screens or referring to lists for many common tasks. Just because a universal technically can do every function doesn't mean it should.
I personal use JP1 remotes which are quite cheap (under $10) and handle every possible function for all my devices, but I don't necessarily program all of them.
EDIT: I just checked, and your Denon has 416 possible commands. I know I wouldn't want that many on my universal remote, but if you do, then go for it. That would be impressive on harmony and an interesting programming exercise on a JP1 remote. I'd probably do 10 or so multiplexed devices on a JP1 remote. That would be the most efficient use of memory.