**EDIT** Just realized how old this post is. I need to start reading the dates.
Series the dual 2ohm for a 4 ohm load, and the parallel all down to a 1.33ohm load, given you have an amp that can run that. You'll be fine. I've mixed different impediance coils before. Given that they are the exact same brand/model, just different VC impediance, you'll be alright. If you want to get down to the technical nitty gritty, you shouldn't do it, however, I know I have without any ill effects. Ever woofer is different, so it will come down to a trial and error to see how it sounds. With some woofers,