We wouldn't want to schedule Ignite on the night of AEC, because we're expecting to have a Social Media Club event, an after-party, and quite likely, an after-after-party.
AEC is slated for Thursday. As I mentioned, rumor has it BIL will be aimed at Friday. Content-wise, Ignite would be an amazing follow-up/pair to BIL. I haven't attended a BIL conference, but it sounds like it's simply a BarCamp format with medium- to long-format talks & discussions. After a day of that, lightning presentations (and presentations that are actually planned/organized) would be quite a refreshing twist.
However, as Francine was implying, Wednesday would also be a good night. Monday and Tuesday are open right now -- and Ignite would make a great week-opener.
There will definitely be something during the afternoon before Ignite, no matter which weekday. Hopefully it's something that will compliment and not detract from Ignite's attendence. I imagine any event would be of benefit, because all of the day's attendees would be well-informed of Ignite.