Yes, you should be concerned. There have been numerous threads by people who have imaging problems caused by asymetric rooms, especially where the side walls are not the same distance, length or material. I would strongly recommend you avoid that situation if possible.
On the plus side, the room ratios and cathedral ceiling are all quite good, especially if you put the the speakers on either side of the "optional fireplace". If you could extend the dinnette wall well past the right speakers reflection point it might work acceptably well.
On the plus side, the room ratios and cathedral ceiling are all quite good, especially if you put the the speakers on either side of the "optional fireplace". If you could extend the dinnette wall well past the right speakers reflection point it might work acceptably well.