I've used a FEA Photon Fuzz 2 before teh XD which has a built in up-octaver which really fills out the high end nicely, and like every FEA pedal it's built like a tank (and sounds great). I've also used a SA UltraWave with success but (like almost every SA pedal) requires a good amount of remote tweaking from a iphone or computer to get some good sounds loaded.Octave and/or Gated-ish Fuzz before it. Find a sensitivity where the filter opens to your liking when playing clean/traditional filter sounds, and then adjust the output level of the fuzz/octave before it so they get the envelope to trigger in a way that sounds good to your ear. There's a lot of preference going on in the question, since the ideal sensitivity and responsiveness of a filter completely depends on what you want. I will say that I find the XD to be a better synth filter than traditional filter. For traditional standalone filter sounds, I like Moog, 3 Leaf, and MuTron stuff more. That said, if you like the XD for just filter sounds, you should be pleasantly surprised by how well it does synth sounds with dirt/octaves going into it...
I find that because of the natural compression any fuzz/dist after the XD filter removes any dynamics, so its def better before then after (unless thats teh sound you want).
I have a Wounded Paw Audio effect loop blender that has the "effected" channel in a loop I can swell in/out, the channel is:
WP send --> Dubterrenea (or FMeron) --> SA UW --> FEA PF2 --> XD --> WP return
I've used a bunch of filters and the XD is still the top pedal based one I can find... I really like the filter in the Moog Minitaur but its a PITA to get it working on external audio, not really feasible on a pedalboard. (I have the Moog MF-101 and like the XD waaay better)