Saw Dust Club Member
Join Date: Oct 2007
Location: Virginia Beach, VA
Here's what about $80 worth of knotty pine and a weekend looks like for your fireplace. Like you, I have a pretty large fireplace and this helped frame it out. For you, I would recommend building up the corners like pillars to wrap around the corners of your fireplace so it flows back to your built-ins.
Since your brick goes to the ceiling, I would probably use plywood to cover from the mantle and ceiling, maybe frame it a little to have a few inches of inset to hang a nice picture or whatever you desire.
Do keep posting pics of your progress. I really enjoy projects like this. Good luck!