Some advice sought regarding surround speakers

I need to purchase new surround speakers for the sides and rears of my 7.4 home theater. Limiting criteria are (1) they must be on-wall mounted; (2) to cover existing holes in the wall caused by my current speakers, they must be at least approximately 16" wide; and (3) because I need four of them and am constrained budgetarily, they cannot cost more than $1,250 each. My current left, right, and center speakers are Revel Ultima Studios and Voice, respectively.

I have read as much as I can about this type of speaker and have initially qualified two brand/model speakers as "preliminary finalists": the Focal Aria SR900 and the Monitor Audio Apex A40. I have no ability to hear either of them. Accordingly, I would be most appreciative of hearing the opinions of others about either/both of these surround speakers -- as well as any others which might also meet my criteria and I should consider.