Love the Hexinverter drum modules...they're versatile, they can either behave themselves or not (and when 'not', they get fun). As for the sequencer, can't really say. That's a piece of gear that really has to be 'to taste', and not something that I think anyone can be 100% objective about recommending. You'll need to sort that one out on your own, depending on your final desired result, how comfortable you are with different sequencing environments, etc etc, and there's a LOT of excellent pattern sequencers out there. Also, with Hex's drums, you might also consider a sequencer that not only does gate/trig patterns, but CV as well so you can make use of the CV ins for pitching the drum sounds. Nice how his stuff gives you that option. Come to think of it...why just one sequencer? Consider: if you use something that's purely a trigger sequencer for your pattern (Acidlab's Robokop comes to mind; it programs pretty much like an old-skool TR-606) and then ALSO a couple of separate CV sequencers (EMW's comes to mind here; 8 steps of CV out, skip switching, and cheap) then you could mult the trigger to both fire the drum module AND step the sequencer, so that next 'hit' actually gets pitched differently. And when you get into that sort of complexity, you're starting to talk about an actual instrument to be played, rather than just a modular beatbox!
BTW, have you considered a suitable mixer for these, or some processing? Hex has a great drum sound-specific mixer (Mutant Hot Glue) with some nice dirt capabiities to beef the sound up. You might also consider a stereo compressor module after that and before your stereo outs to punch up the dynamics and get more presence.
Sounds like it's coming right along!