I came about a pair of Cambridge Newton S200 rear channel speakers. I am currently using a pair of Yamaha outdoor speakers for my rears. I was noticing that the speaker response is only to 10K. Do the rear channels need to go higher than that? Would they be good for Dolby Digital 5.1? I am using a Boston VR920 for the center and a pair of Legacy Focus for the front mains. Thank you for reading.