I think REL's high level connection technology is just incredible. This allows them to play more like woofers and they seamlessly extend the bass if set up properly. I added two REL SHO's to my system and it was a game changer. I would recommend two large REL's to create a great sound stage.
My friend had an SVS subwoofer and it sounded very boomy. Great for a teenager who loves to hear a pounding bass sound. REL's play different styles of music incredibly well.