Ok. You have one of those typical horrible totally non symmetrical and off center situations with a giant opening into other rooms. Its a pretty bad room to do this in. But like most, it is what it is. So short of building a dedicated room, you will have to do what you can to get the best sound.
What is above this room and which way do the joists run?
If you must use reflective bounce atmos speakers, I would simply not use an atmos setup. Either put them into the ceiling like they should be, or skip atmos and just use a 7.2 setup. To do it right you will have to cut some holes to run the speaker cables, patch them up, and repaint. But it's worth it and if you simply take the time to do it right yourself, you can save a lot of money.
I would consider this:
1. Remove your fireplace completely, or re build it in the center of the same wall, thus centered in the room. This will require some work, time, and expense, but you will at least keep the fireplace which has resale value (even though nobody ever seems to use them). You should be able to use the existing chimney vent without dealing with new chimney issues which are too expensive in your situation. Then either put in a 65 inch television above the fireplace on a mount that will allow it to swing down in front of the fireplace (they do make these kinds of mounts, motorized or manual), OR, put in a ceiling drop down projection screen and purchase a projection system. If you keep the fireplace and center it, you would actually increase the resale value of your home.
Otherwise keep it the way you have it.
2. Use in wall speakers (same brand as your main speakers, whatever that may be) for left and right surround, and rear surrounds. You have spaces to do this. Keep the speakers at the same level, and keep the final position of these so that the tweeters in them are 1-2 feet above seated ear level. Take the time to run the wires in wall. Yes, it takes work to patch and repaint. But its worth it in the long run.
3. Get two inexpensive SVS subwoofers instead of one. Since the 1000 is already the cheapest, yes, its going to cost you more money. But two always sounds better than one especially considering you need the extra power because of the giant opening to the rest of your home. Put the subwoofers in opposite locations in the room, or anywhere that they are most unobtrusive.
