One big problem is that many don't measure their system's response using pink noise and an inexpensive analyzer system like audiotools (free by the way) from their listening position.
Using a test CD like Stereophile's you can play back pink noise and look at your system's response. The room has a major effect also. If the response isn't flat from 20 hz to 20 khz, it will show the dips and hills. You want to at least start with a completely flat response at all frequencies from 20 hz to 20 khz.
many manufactures try to fool listeners by either boosting bass response or lowering mid range response to give the illusion of great bass response.
I know many advocate subwoofers to be installed. However, in my opinion, if your system (speakers included) actually give you a flat bass response with the other frequencies, then your system does not really need subwoofers and is doing its job.
That's not to say it won't benefit from subwoofers or equalizers. This is where room treatment comes in first, then equalizers (there are some really good ones out there), to either boost or cut certain frequencies.
Try it Get a test CD with pink noise, and use the Audiotools app. There are others also. But free is free. See from your listening position what the response actually is. You might be surprised.
Too much bass? Too little? etc.
enjoy