I wouldn't spend the extra for the SE's for rears. The SE is just a beautiful speaker, and definitely a step up from the 1.3's - I'd spend the extra in a second for the fronts of a music system. Unless you listen to a lot of surround music, I'd save the money. If you do listen to a lot of surround music, then it is probably worth the extra money. Or, if you listen to a lot of surround music and have the space, you might want to use 2.5's in the rear as well.
I, personally, use the 1.1's in the rear. I have found them to be easy to place relative to the 1.3's and they are one of my favorite small speakers. That might save you even more money.
I listen to a lot of 2-channel music and watch a lot of movies. -Kirk