So, I have a DT50 and Pod HD500, and I use the L6 Link between them.  I would say that if you cannot find "a sound" that you like with the combo, that you're not looking deep enough.  If you're having trouble doing it yourself, use some of the downloadable files, and then typically what I do is even tweak those.  We all have different ears, different desires for sound, and therefore you need to "make it your own".  I would say that I've discovered/re-discovered at least 6-7 times "my sound" on my combo.  Sometimes instead of practicing, I just play with sounds.  I usually start first with the amp, then add some reverb, and then go from there with desired sound.  I have in the past used a Cab setting, but now I go without.

I did add a THD Hot Plate, and think it really brings out my rock/metal tones, though using it, it is harder to get my clean sound, though I have a "good enough" clean sound for me (as I'm not a big clean fan anyways).

Never played with a M9, but I've been really happy with the FX in the Pod HD.  It's just a matter of playing.