I agree on the SVS sub. It’s easy to integrate and has plenty of controls to dial it in. In my situation it was almost too easy.
Replacing current sub with another
I am in the process in replacing my current sub with something with better control, meaning tuning and integrating. My option would been a SVS SB-1000 pro. Keep in mind I have a very small room and really the Vandersteen 2ci are more then enough for the need of any music. I have a sub not for output but for quality and and response. I have the tools to tune and integrate the sub with the 2ci so that is not a factor. I currently have the HSU STF-2 and is a great sub but it only has the basic controls so I am limited.