TSi300's as Rears?

My current setup...

I have Polk TSi500's in the front and a Polk CS20 center.

I currently have no sub yet- will puchase last!

Right now I am considering getting TSi300's for the rear. Are these basically the same speakers as the TSi200 bookshelfs? As far as I can see, the only difference (other than the height difference) is:

The TSi300's have a freq response of 35-25KHz compared to 43-25HKz for the 200's.
The TSi300's have a -3dB freq response is 47-24Hz compared to 50-24 for the 200's.

So I guess the 200's have a bit better range on the low end? Rather than putting 200's on a stand in the back, I was figuring to just get the 300's instead- if they are appropriate...

Thoughts?