I'm in pretty much the same situation as you. What I've learned from other posters here who've tried it already, we're both going to need to get a preamp of some kind. The JuicedLink preamps get pretty good reviews, and if you go that route you'll need one with meters since BMD hasn't put audio meters on the camera (yet?). The A-box would get you the right connection, but probably not enough gain to be of much use. You do get much better sound quality even with a Zoom recorder if you put a good preamp in front of it and keep the recorder gain low, and use the preamp when you do need gain.
What I don't like about the JuicedLink preamps is that they're very specific to digital SLRs, which means that they provide very few options as far as output, that is to say one option, and it's not a professional grade option. The Hollywood sound guy that did a presentation for ASMP in Seattle about 18 months ago said that one of the reasons that production companies avoid the 1/8th in connectors is that they're not reliable under extended use. BMD provided a pro grade connector option, even though it's a little bit uncommon on recording devices. Pro synthesizers usually have 1/4 inch jacks like the one on the BMCC.
I'm actually leaning toward a Sound Devices MixPre-D, because as far as I've been able to ascertain, it has the best sound quality out of the portable field mixer/preamps out there, plus the analog to digital stage and I/O flexibility make it flexible. It's pricey, but probably worth it in the long term, to ensure that the sound is as good as the picture with the BMCC.
Hopefully this will encourage someone more knowledgable about it than I to respond
