best scenario is to have the center and the left/right speakers on one level plane across the front of the viewing area. obviously, that set-up is not avail for most, so its OK if you basically just make adjustments for what you have.
i think the two best options for you are to, (1)mount the 22's out to the side of the TV. total separation between the left and right should be anywhere from 5-7 feet. or (2), place the 22's on the taller speaker stands on either side of the fireplace, once again with a separation of 5-7 feet. the center will be fine on top of the mantle in both scenarios.
another thing to be aware of, if its a working fireplace. some people with plasmas/lcd's/flatscreens, that place them over fireplaces have had issues with the heat and smoke rising up and discoloring the screen. now, not everyone has had this happen, but i know a few have mentioned it. so, just be aware that can be a problem. one good way to tell is, look at the fireplace as it is now. if you see mild discoloration on the bricks/front/mantle directly above the firebox, you might have similar issues. just food for thought.. i would hate to see a $3-4K TV get melted..
bigjohn
