I personally like the pairing. I usually use my 4's with Comply tips because I don't like the highs with the silicone tips. Often this attenuates the high's somewhat but still presents what to me is a "natural" presentation of music, though some folks may find it to be a boring or un-involving sound. With the DX50, even with the Comply tips, the highs have some more sparkle to them though the sound generally remains balanced. I could do with some more bass but it's there (I haven't messed with EQ though to see if that makes a difference). Nice soundstage as well. So I think if you like the Westone R sound in general you'll probably like the pairing with the caveat that, at least to me, it's a brighter sound than I'm used to getting out of them.
I want to add that I think the pairing works better with the X3 - a warmer sound, though at the expense of a more intimate soundstage.
Edited by frankrondaniel - 10/9/13 at 11:49am