What is the most dramatic way of increasing a speaker's Bass and Low mid?

I'm going to have room treatments done, that will most certainly require professional measuring equipment, and someone who knows how to use it.

Moving your speakers closer to the corners will load the low frequencies and increase their volume.  Too much and it will muddy vocals and destroy the stereo image.  For a 36" tall speaker in a 12' X18' room with 8' ceilings, start with theses numbers to increase the bass: 14" from wall to speaker face, 22" from Woofer center to side wall. The next position, pull the speaker out to 22" and or pull it in to 27" from the side wall, or both. Each will reduce the bass a bit.  These numbers aren't 'woo', they are basic room acoustics - physics. Pushing the speakers to the walls and corners increases the room 'loading' of the woofer, the ratios minimize standing wave (eigentone) reinforcement. You can also download a spectrum analyzer from Google Play like 'Spectroid' and run pink noise through your system to get a rough idea of the frequency response for a given mike location.  But, by all means, listen.  The tools and equations are there to inform your decision, not make it.

Moving your speakers closer to the corners will load the low frequencies and increase their volume. Too much and it will muddy vocals and destroy the stereo image. For a 36" tall speaker in a 12' X18' room with 8' ceilings, start with theses numbers to increase the bass: 14" from wall to speaker face, 22" from Woofer center to side wall. The next position, pull the speaker out to 22" and or pull it in to 27" from the side wall, or both. Each will reduce the bass a bit. These numbers aren't 'woo', they are basic room acoustics - physics. Pushing the speakers to the walls and corners increases the room 'loading' of the woofer, the ratios minimize standing wave (eigentone) reinforcement. You can also download a spectrum analyzer from Google Play like 'Spectroid' and run pink noise through your system to get a rough idea of the frequency response for a given mike location. But, by all means, listen. The tools and equations are there to inform your decision, not make it.

I'm still in the flip-phone era, but yes, this is a GREAT way to add measurements to ears.  (Google says there's one for the iPhone, too)

Srsly, this is cheap/free (the PC-based REW is free, dunno about the phone apps) and should be what you start with.

Second REW.  You can pick up a USB phantom mic for about $50 - $80, Dayton Audio comes to mind.  I don’t know if REW integrates with an app, now, but Dayton does make app capable measurement mics.  

My experience with REW is what led me down a long path to maximize my system.  Inclusive of what’s already been shared, getting your speakers positioned to where they sound the best to you is critical, prior to measuring.  Chasing placement to minimize spikes/curves/room anamolies will make you bonkers.  I’ve done it and it’s futile.  Once you’ve set them, then run REW.  What it will show you is what needs to be tamed.  Mids/lows, again, boosting them may not be what’s needed, possibly there’s too much low end and taming it will allow the midrange to punch thru.  

Once I had my measurements, I critically listened to all my favorites for a week or so.  Then sent my measurements off to an acoustic treatment company to build me a set-up, specific to my room and the measurements generated.  I used GLK Acoustics, but there are plenty out there to choose from.  It was night and day once I had them installed.  I had read numerous posts on here before, regarding room treatment and just didn’t really pay it much attention.  Now, it’s one the lowest cost applications I’ve used in my system.  I should note, I didn’t read thru the entire thread, so it may have been covered, that your room (aka significant other) is not open to panels being hung; which is completely understandable.

Post treatment I listened for another month, it did sound exponentially better with the treatment, but I still felt I could squeeze more out of it.  Enter DEQX.  It does EQ, but more from the perspective of minimizing frequencies that shouldn’t be there, due to the speaker interactions with the room.  And that’s the big difference, addressing the room and then addressing the characteristics of the speakers, in relationship to the room.  

I’ve used the McIntosh MEN-220, which is based on the Lyngdorf/Room Perfect algorithms/software.  It did make a difference, huge difference.  But, it had some funky glitches with REL subs and the amp I was using at the time.  Additionally, it’s very pedestrian; meaning there’s not too much user configuration involved.  If that’s what you’re after, it’s wise to go with a unit that is user friendly.  DEQX is not, to be frank.  It takes some heavy lifting to get it configured; which I was successful in getting it to about 95%, but ended up hiring a DEQXpert to set-it up.  Took about an hour and cost $400.  The DEQX combines the room and speaker measurement and makes corrections based off of that, which gets very complicated and confusing if you haven’t been thru it.  

Net-net, a room correction unit will bring focus and clarity to your music.  I’m not a big believer in EQ’ing, but am a staunch supporter of utilizing it in conjunction with phase adjustments to improve existing rooms and speakers.  

Most dramatic way is replace speaker with one that has more frequincy extention while Garry Moore The Loner plays on a distant radio.