I don't have any specific experience with either sub mentioned but I own a very similar model. The REL T3 which is an 8" driver with an 8" passive radiator. While it is fast and tight, it lacks deep bass. It's rated 6db down at 30hz and you can definitely tell. I figured since I was using it only for music that I wouldn't miss the lower notes but I do and am now looking for something else.
