Not knowing the size/dimensions of the room, and equipment associated with driving the speakers, it is difficult to make any suggestions. You say that you have 2 channel already handled, so I assume that you won't use these for music at all except for maybe concert videos? Or will you be listening to SACD Surround/DVD-A 5.1?
My suggestion is spend some time at the dealers listening to the speakers that deliver the most impact. You may find that the CM series or the 600 Series will fill the bill and save you some money in the process.
I think that (of course we don't know yet what you are using or plan to use) that the pre-pro and amplification play a very big part in the delivery of accurate and involving surround sound. From my experience I would rather have the fronts and rears match in size or be very close in size than have bid fronts and small rears. I feel that DTS-MS utilizes the rears more and that I lose bass response in the rear. Also since I listen to SACD/DVD-a 5.1 I would get a more surround envelope that I prefer.
But you may have a different taste that I do. And if you are utilizing 7.1 the the larger rears would probabaly not make sense. Just offering my opinion.
My suggestion is spend some time at the dealers listening to the speakers that deliver the most impact. You may find that the CM series or the 600 Series will fill the bill and save you some money in the process.
I think that (of course we don't know yet what you are using or plan to use) that the pre-pro and amplification play a very big part in the delivery of accurate and involving surround sound. From my experience I would rather have the fronts and rears match in size or be very close in size than have bid fronts and small rears. I feel that DTS-MS utilizes the rears more and that I lose bass response in the rear. Also since I listen to SACD/DVD-a 5.1 I would get a more surround envelope that I prefer.
But you may have a different taste that I do. And if you are utilizing 7.1 the the larger rears would probabaly not make sense. Just offering my opinion.