What you have is an excellent subwoofer, but due to the issues in all small rooms, one is never sufficient for more than one listener! I would recommend getting another, or similar, 10" sealed design.
The e112 is not an improvement in anything.
You've clearly spent some money on your system, so if you want the best out of it, you need to get the bass right in every seat. Dual subs will be an improvement, quad is most enveloping. And when you are running quad subs, it becomes quite clear that the diameter of the cone is meaningless. So it's great that you already started with 10" subs, because their petite size makes them easy to hide!