Not that I can answer your question, but it make me think a bit because would one really want as present a filter as the Moog Ladder filter in a polyphonic synth, if you can choose only one analog filter?
Personally I'm not so sure I'd want the MOOG filter sound in a poly because when the low end is so present as it is with the Ladder filter, not taking much volume out when the filter close would quickly make the low-end muddy when several voices are going at the same time especially in the lower frequency spectrum.
Thus I would not want a ladder filter on the X either, since this is a polysynth... also it's mostly meant to filter samples.
I'd say that the ladder sound (in my opinion) lend itself best to monophonic basses and lead sounds, and I'd rather go for one of MOOGs monophonic synths for that when it comes to the ladder filter.
I also heard Amos talk about why they put in a State Variable Filter in the MOOG ONE, which was exactly because the ladder filter has too much presence... in the ONE we have the luxury of two analog filters to take care of both, which is cool, but if it boil down to having only one, I'd certainly hope that the X does NOT have that same presence unless there are some other means to ease out on the low-end somehow...
In fact I often have problems with the REV2 bank I'm doing right now in the low end, where some sounds simply get way too loud and boomy in the low end .. .I'd actually have liked to have an analog hipass filter in the REV2 as well to remedy this problem from time to time... it's a nightmare with huge pads and atmospheric sounds in some cases, especially the more open the filter is.