You don't lack bass, you have too much treble

@mijostyn very good points.  I have bass traps in the corners behind my speakers, they actually help greatly with the room. I've listened with and without them and the really help

I also use a Krell KBX electronic balanced crossover designed specifically for my speakers (incorporates some wave shaping circuitry) with low and high adjustments that I use to tune slightly. Trying to get the flat response first and then adjust slightly for effect.

I am sure that I can do more.  Room treatment is hit or miss with no refunds if you miss and most are seriously ugly.  But, sometimes worth a try.

I know McIntosh labs actually have a equalizer that might help that has balanced in and outputs.  I am looking into that or some other.

But, I'm pretty much "there" with my system otherwise. I just replaced the panels on my Martin Logan Monolith III speakers and upgraded the woofers to the Pearless woofers.  Nice!

Those speakers are still outstanding and with the Krell crossover, I don't hear any gaps or timing issues between the panels and the woofers.

I'm sure subwoofers may help, but I don't feel I'm missing anything. Especially when I go to my dealer friends and listen to my music on their equipment with subwoofers.  

But, one never knows whats in the future.  I've tried subwoofers added before, and couldn't dial them in correctly to the extent they weren't hurting the sound more.

But I know there are some really nice subwoofer systems out there.

Also, My Audio Research REF 10 pre-amp is simply outstanding an well no, not changing that anytime soon.

Thanks for the suggestions,

enjoy

Another side of the same coin:  If your system is well-balanced and you add subwoofers thereby extending the response an octave or more on the low end, the net result may no longer sound balanced.  In this case, it can make sense to flex your DIY muscles a bit and add a rear-firing tweeter whose response is tailored to filling in the top octave where your main tweeter is beaming. 

In my opinion.

Duke

@audiokinesis My favorite all time speakers, the Snell A/IIIs used that trick, also contributed significantly to imaging.

@erik_squires, Omigosh yes, what a brilliant-in-concept and magnificent-in-execution speaker the Type A/III was! In 1988 or thereabouts I submitted a DIY construction article to SpeakerBuilder Magazine that was essentially a variation on the Type A format, but unfortunately they weren’t interested.

@mahgister *S* Just wanted to register some concern, but thought your usual approach to items audio would prevail...

Having had some 'sudden surprises' with headphones over my times, I've taken to initially park them 'off ear, dj style' if doing something novel.

Beats throwing them across the room...*L*

Best & better back 'atcha', J