Upgrading From Kodak ZI8 - Need Advice

We make instructional videos indoors using a ZI8 and AT3035 microphone. I'm generally happy with the results:

http://www.getvisiblevirtually.com/online-business-manager/

Questions:

If I spent $100-200 more on a camera would the results warrant it? What camera would it be? I've also looked at a Sony HDR-CX190 but it doesn't have a microphone jack.

I'm looking at the Sony Bloggie Sport because the .mp4 output format will work without conversion in Sony Movie Studio Platinum 12 (the ZI8 outputs .mov). Am I being foolish to change for that reason alone?

How do I make 2 microphones work when my wife and I are on camera together?

Any other advice you'd care to give.


Thanks very much in advance!

Yes, it comes with an AC adapter.