It has been my experience that placing resistors as padding in the high output of a two way seems to dull the sound adding artifacts. It may work out good for you so give it a go being you got most of the parts handy.

Well that was a fun exercise. R1 is not needed for this circuit with the F15.  I tried 2.2, 4.3, and 6.8 ohm for R2 and all have a different effect, with no clear winner.  The bass is very natural and integrates very well between the w15 and f15.  However, just loses the magic of the amp straight to the speaker.  A reminder of the detriments of adding unnecessary parts to a circuit and the tragedy of the crossover.  I could see how someone that never experienced the F15 on its own could enjoy this crossover design implemented into the Liionidas speaker.  But the F15 alone driven by a SET amp is still superior.

For now I'm back to biamping.  I've traded the XLS1002 for the older XLS1000, preferring the 1/12 slope on the low-pass over the steeper 1/24 of the XLS1002.  Currently crossing over the W15s at 50 hz, just picking up the low dropoff point of the F15s.  For softer music the F15 is still just magical on its own.  For classical, electronic, and rock the added weight of the W15 can add some room shaking realism.