Hope you don't mind my "input".
I heard the X several times & sold one pair. I listened at length in privacy to the 60.
There are so many intrinsic differences in the two system's architecture that a linear comparison is literally impossible.
The 60 is mandatory biamp & active xo, the X is single amp or biamp passive or active. The 60 can be employed w/ one mono sub up to as many as your room can hold. If the X were biamped (NO outboard sub), each channel would require a seperate sub channel. The X could be biamped w/ it's own passive xo while the 60 requires an active xo for its sub. Of course, an outboard active sub can be added to the X or any speaker. Adding a sub to the X makes the comparison either more or less linear depending on your point of view.
The 60s bass architecture is dictated by the fact that it splits the bass between two systems, the lowest bass up to about 70 Hz (which can be in mono OR stereo depending on your room & wallet) then the stereo mid-bass covering from 70 Hz to 260 Hz (about middle C). The X employs one "system" (PR, active 12 & 10) from the bass up to 260 Hz.
The 60 allows one to tune out, or introduce a beneficial notch, at the most common room mode, which is about 70 Hz for an average 8' ceiling. This is accomplished by selecting a proper xo pole for the sub's active xo, some frequency below the cutoff of the 6.5s. (I hate reminding readers that I recommended this several years ago
)
The above gives a huge, unmistakable advantage to the 60, but also adds to complexity. As someone who has worked a lot w/ subs & VMPS, I think the 60's bass archcitecture is win-win. Though others may disagree, & I absolutely respect their opinions, I personally think the 60s bass architecture works perfectly well.
The 60s VSS goes deeper. Frankly, IMO, the Xs cavity, after subtracting for the largish midrange subenclosure, seems a bit small for the bass drivers employed. The 60 utlizes three 6.5" midbass drivers in a sealed system, which both theretically & actually gives better performance throughout their range vs. the X's reflex 12" + 10". Middle-C is approximately the xo point to the mids. 260 Hz isn't that high, but the first-order slope means there is significant output well up into the midrange. Obviously 3x sealed 6.5s have a large advantage in musicallity, etc.
The X has no CDW, standard on the 60. Both systems employ 6 mids, though the 60s CDW attenuates midrange output by 1.5 dB. The 60s larger tweeter has about 4 dB more treble output.
Do a search to read about the audible advantages of the patent-pending CDW.
The 60s open-back wing & adjustable damper completely eliminate the back-wave distortion inherent in the X, & they allow the user to tune the back wave output to their heart's desire.
Finally, the 60 employs a standard OXO (outboard xo). Ditto a search to read about it's audible advantages. Less smearing, higher resolution, etc...
I'd have to summarize it's a very unfair advantage for the 60 in every audiophile & musical category. The X is no slouch, but time marches on (I'm the first to admit that not every newer product is necessarily an improvement, even in vmps land.)
PS, the 60 may be more complicated to setup but is much lighter than the X to move about. My friend & I are reasonably certain the Wing section itself weighs only about 90 lbs (abaove the 6.5s), less than Brian's 150 lb estimation. We'll all know better after it lands on the certified vmps audiophile scale.
