Sealed designs are usually much better for mid-range application than ported. Porting is only suggested if you must extend your speakers.They don't go down all that low because they are sealed boxes. Most speakers these days, like the MTS series, get their lower extension by using a ported design. Lets you go much lower with the same size drivers/box.
Now sure why the S series are all sealed designs, perhaps for simplicity (it does require more work to design a good ported speaker). Regardless, it means less extension with a given size of driver.
As to the original poster, no, sorry, I have M-series SVS speakers.