The X1 wouldn't be an ideal match to the E09K due to high output impedance, since it may slightly alter the frequency response of the X1 (maybe more/less bass, and less/more treble, etc). However, the effect may be too subtle to pick up, and/or it may actually make it more enjoyable. All in all, I suggest trying the X1 off the E17 first, then trying it with the E09k and see if the E09K affects it negatively in comparison to the E17 alone.
The E17 alone is good enough for the X1 in case you have problems with the E09k.
The X1 isn't reliant on powerful amping, and I used it with the E17 with great results, even after having used the X1 with the much, much more powerful Compass 2 for awhile.
The M/M stack should be a very good combo for the X1, due to their cleaner, slight treble orientation compared to the Fiio which is on the warmer side. The X1 can always use some extra control in the bass, which I believe the M/M stack will do better.