can subwoofers make things worse?

Rel and Kef are great. I currently own older pair rel subwoofers in my 2.2 audio system.

I would drop SVS. Not good at all unless you want a one dimensional boom.

pair is needed. I ran a single subwoofer for awhile and when I went to two it was very different and much fuller sound. Synthesizer bass effects became much more dramatic when panning between the two speakers as a lot of modern music does for effect. Drums sounded fuller and became more dimensional in the soundstage. 

@soix

have you ever compared subwoofers? Apparently not.
I have and stand by what I said per experience and am not some fan boy.

here is one review where the reviewer is kind to SVS and all its like brethren substandard like JB Audio, etc… Buy SVS if you want one dimensional boom that impresses the simple folks