This isn't a critique on the original poster, just a reminder that different sound signatures are for different listeners. I don't hear a muddy bass at all with the Momentum 2.0. I find it detailed and there when it needs to be there. There's no masking of other frequencies with my iPhone 6, iPad Air, and Macbook Pro. When I add my Fiio E6 using the bass boost feature, I can't say the bass is thrilling, but there's signal loss with the extra connections and dual-amping going on. Using an equalizer in say Spotify or on my Macbook, I can get the sound as full as I like without a sense of muddiness to my ears.
Sparkle-wise, there's more than enough for me. The treble is detailed without being overly-analytical. There's little of the splashiness that bothered me with the original Momentum over-ear. No sibillance to be sure, but I could stand for the 2.0 to be a couple decibels lower in treble in relation to the bass, as I have basshead tendencies. This is source-dependent... hardware and software. I also found the original Momentum mildly boomy, and just not as natural sounding across the board.
I find the 2.0 handles whatever I throw at it, and I can tune it to bombard me with bass or detail, and it answers accordingly. Straight from my Pad Air using Rdio at the highest setting, it's not as lush as I'd like, and while the iPhone 6 is an improvement, it's still somewhat disappointing. Switching over to Spotify, pumping the bass a little and lowering the treble, it's golden. I find Apple DACs overly bright in general.
I auditioned about 40 headphones before sticking with the Momentum 2.0. It gets a lot right as a portable for me... comfort, natural clean sound, style, transportability, and very very little leaked sound. My other favorite portable is the Audio-Technica WS99. They have some cons (build, mid-bass bloat), but they're lush and a steal under $200. I'm about to audition the Oppo PM-3, and it'll be interesting to see they compare to the Momentum 2.0. If they roll-off the treble a bit more than the Sennheisers, I might make a switch, so I'm not as reliant on equalizers, amps, or an external DAC down the line. But muddiness and missing sparkle I don't hear. Just my opinion, and this is in relation to the specific 40 or so others I've tested. I do thank the original poster for sharing and getting me thinking more critically about whether these work for me.