Here for triple-flange eartips: http://www.meelec.com/product_p/tipset3-tf35m-mrg-cl.htm
They'll cost you the outrageous sum of $4.99. Nobody seems to pay too much attention whenever I mention these, but the difference they make is fantastic, especially when used with phones that are as good as the Denons. Cheapest possible upgrade you can make. I have six sets of canalphones with these types of eartips attached, three MeeElectronics M6P Sports, Shure SE215, Ultimate Ears SuperFi 3 Pro and UE TripleFi 10 Studio, and every set of phones gave me problems getting a proper seal in my ears, with reduced bass as a result. Until I tracked down triple-flanged Eartips that would fit. It depends on the acoustic tube on the phones; lots, like the UE's, and, I think, the Denons, use a large diameter tube, which the link above takes you to. Shures use a small diameter tube, same as Etymotics, so you can use the Shure triple-flange tips on Etys.
Honestly, just getting some of those will transform canalphones, and, unlike foam tips, they're dead easy to clean, just by folding the flanges back and wiping with an antiseptic wipe.
My Etymotics have full custom eartips fitted, a luxury at £90 when I bought mine, but I was left feeling totally underwhelmed by their performance, especially after many people said how good they were.
I hadn't used mine for around three years, until a week or so ago, when if had an idea, and had a search in the App Store, something I should have done ages ago. The stock EQ on iPods, iPhones, etc, is pretty rubbish, so I looked for one that allows a custom EQ to be set, and found one called EQu, which is brilliant, and it's transformed the Eties, giving them some proper bass at last. Not the sort of bass that the UE's, Shures and M6p Sports deliver, which sometimes feels like they're trying to inflate your head, but pretty respectable.
Highly recommended, you can tweak and fine-tune the EQ curve to your heart's content.