Hi! My husband and I are shopping for a new King size bed. I am 5'6 and 180. He is 5'11 and 170. The mattress we currently have sinks down in the middle so we frequently roll towards one another while we are sleeping. He has sciatica on his right side and also middle back and neck pain. I have lower back pain and on occasion have severe pain in my upper back between my shoulder blades after getting out of bed in the a.m. He prefers a firm mattress, and I prefer a slightly soft one. What type of mattress would help with our pain?