I just recently upgraded my receiver to the HTR-5590. Now, I'm thinking about upgrading my speakers. I bought a package of JBL Simply Cinema Series SCS-135 speakers a few years ago. I'm thinking about replacing it one piece at a time since I'm on an extreme budget. I bought a sony sub already right after I bought the package since the sub that came with it really was bad. Now, I'm thinking about replacing the center channel. I know my satellites are 8 ohms. I was considering the Yamaha NS-C444 center which seems much better than my JBL and cheap (which is my price range, cheap!). My concern is, I noticed it is 6 ohms, will I have a problem mixing it with my 8 ohms satellites? Do I need to stick to same ohms alll the way around? I am also open to other suggestions but I really don't have more than $200 to spend. One other question, my new system is a 6.1 which before I only had a 5.1. I'm thinking about buying an extra speaker for the rear center. Is the rear center just another satellite or is it like a regular center channel? Thanls!