Kannagi DVD 1 is presently at #67 in DVD popularity at amazon.co.jp, #12 in TV animation category. And it was only released 11/26.
Link here.
DVD 2 is at #25 overall, #3 for TV animation and it doesn't release until 12/17, so those must be pre-order numbers.
Not sure what amazon sales say about anything, but
Kannagi seems to be doing well.