Perhaps you could be a little more specific. Say for example:
I have $800 to spend.
I have an integrated amplifier.
I like the sound of my monitor speakers, I just want to extend their performance.
Sure, there are other sub manufacturers, but you have given no indication of how their offerings could give a superior solution at the given price point.
If someone were to ask how to get better performance from their honda civic and they have $1000 to spend telling them to go trade for a 911 turbo doesn't really help them.
I have $800 to spend.
I have an integrated amplifier.
I like the sound of my monitor speakers, I just want to extend their performance.
Sure, there are other sub manufacturers, but you have given no indication of how their offerings could give a superior solution at the given price point.
If someone were to ask how to get better performance from their honda civic and they have $1000 to spend telling them to go trade for a 911 turbo doesn't really help them.