Z,

If you post a picture, we may be able to help you better.

You could run the speaker cable along the bottom of the fireplace if it is elevated. You can purchase 105 degC-rated, 12AWG speaker cable at Home Depot for less than $1/foot.

Brick walls certainly are brighter but I wouldn't sweat it until you actually have a chance to listen to your set-up. I have a very bright room and I am happy with the sound.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated