I'm not voting for the X5. I've never tried it. I'm not planning on trying it because I don't know what it uniquely brings to the table (relative to the 846) and user experience.
The Sony ZX1 is the more interesting of the boutique DAPs, I've tried. It puts stronger priority on frequencies panned to the right and left whereas most other players have better clarity in the center. It's not trying to be an all-in-one that can drive your full-size headphones as well as your IEM.
Perhaps the new AK line will be worth a look since it features Android. Maybe it will be hacked to allow software from the huge brain-trust of people who have been working on software players and DSP development in the Android environment for years. Why exclude those options? I'd rather exclude the boutique DAPs than limit my choice of sound to only the one decided by HiFiMAN, FiiO, iBasso, or whoever.
I'm casting my vote for a hackable Android device that will let you install any number of music players and digital sound processors. It's about software development (IMO). I don't think it's about putting together hardware pieces ( like brand named dual DAC configurations and more powerful headphone amps), particularly to drive an earphone like the 846.
As for the DX90, it is a fine portable player. For those who like to plug their headphones up to the jack and press play, the DX90 is better than most smartphones (I've heard) with stock software (including the Note 3). It hasn't crashed once since I've had it. It gets a little slow at times. There's a popping noise when the amp comes on. It has very little hiss (not even worth mentioning). It's quieter than the ZX1 (in that regard).
Whereas the DX90 sounds a little better than my iPod Touch 5G (using stock player). I'd choose the Touch 5G (with Onkyo player) over the DX90. The Touch can do many more things and is very stable, fast, and less expensive. These boutique DAP makers are wasting my time (and I'm going to stop letting them). The Note 3 (with V4A and Poweramp) sounds better than all the DAPs I've tried to date (while doing everything from phones calls, internet, text messaging, taking pictures, GPS, etc (using 30 to 50 percent battery per day).
There is no comparison between the DX90, HiFiMAN HM-802, Sony ZX1, FiiO X3 with the 846 versus the third party software on the Note 3 (namely Viper4Android). If someone is talking about sub-bass with any of the above boutique DAPs, they don't know what they are talking about. They don't know what sub-bass is because it is not coming out of those devices at audible levels.