Diagnosing inadequate bass in an audio system.

I use a frequency sweep such as this one from Audiocheck.net to check bass response by ear.

Erik, I wouldn't say my question is too broad. I would say that my problem could be occurring due to innumerable issues. So, in such a case, how do I narrow down the possibilities to a finite number of sources, so that it is easier to then pinpoint the source or sources of the problem?

Is the audio version of:

My car is making a sound, how do I figure out what's wrong with it? 

And impossible to answer well without a class in auto repair.  Giving specific information about your gear, your experience, and room however helps those who want to help you target their energy.  It's considerate when asking for help. :)

@amitb - seems to me that the best educating as to what the best bass should be for you should be done by your ears and your brain. Nobody else can tell you what sounds best to you, and if it doesn't sound best to you, who cares what somebody else thinks? What is not enough bass for one person could be waaaay too much bass for somebody else. 

The Audiocheck.net site recommended by @yage seems like a good place to start.  I have Stereophile's Test CDs and typically use similar tracks from Test CD 2, which used to cost about $12 but can now be purchased for $50 on Amazon! 

Checking by ear can be helpful but if you are in the beginnings of building a system, it may be beneficial to somehow make a record of your in-room response so you can compare with changes that occur after future system upgrades.

Regarding bass, I never quite achieved satisfaction until I added dual subwoofers that I run in stereo through separate R and L line-level outputs.  They roll in very low (55Hz max) and augment my large standmounts that deliver convincing bass down to about 40Hz.  To free up those main speakers and my amplifiers from trying to reproduce the lowest bass, I recently added a Marchand XM46 Passive Line Level Balanced Crossover between my preamp/buffer and my amplifiers, which rolls off my main speakers at about 45Hz.  Incorporating the crossover and the two powered subwoofers has resulted in realistic, dynamic bass response throughout the room that I can adjust for individual source content and listening levels by using the level up/down function on the subwoofer's remote control.  I plan to add a third matching sub at the back of the room that will be run in mono through a summed L/R output. 

Below is what the designer of my Aerial subs had to say about multiple subwoofers:

The SW12 system is extremely flexible. One SW12 provides satisfying high quality mono bass. Two SW12's produce more realistic stereo bass, higher levels, and better smoothness. Three SW12's add front / rear information and truly envelope the listener in bass. Large 4 or 5 channel systems are even more realistic and impressive. Unified hook-up and remote control are provided.