Installing Facebook comment plug in without loosing all previous wordpress comments?

From all I could research on this, there’s just no way to “merge” existing WP comments onto the Facebook Plugin. So my solution for this problem with a client was to style wordpress comments exactly like fb comments, except that they always appear below all other fb comments.

Then, by default, i leave the fb comment form loaded on the single page, and at the bottom of everything i have this “don’t use facebook? comment here” button, calling WordPress’ default popup comments window.

This way you can still have both functionalities and still privilege fb comments.

EDIT:

I didn’t realize you were talking about plugins in general, and not about the actual FB Comments App. My solution was to install it by hand, on the actual comments.php instead of looking for a plugin. It turned out to be easier than to find a plugin that would do it exactly as i wanted.