I personally don't think think you will get all what the C4's are capable of. You will loose a lot of depth by placing near the rear wall. My listening area is just about what you have now and when I did an in-home demo of the C2's (currently have the C1's with a sub) I found I lost a world of depth and they sounded way too forward until I took out all of the toe-in. That helped but still didn't quite sound right. Remember I have the C1's as my reference. At my dealer I demoed the C2's and C4's and they sounded fantastic at his place. His room is approx 15 X 25'. Another thing I noticed is in my home I sit approx 1' from the rear wall and maybe for that reason I didn't really care for the sound as much with the larger C2's.
What were the dimensions of your old room compared to the new one??
You will have to try it and post back. I too if I had the C4's would hate to part with them.