Talk to me about a second pair of monitors

Are you looking for a second main pair, or something different? I use a pair of reftones as a scond reference, and I love working on them. Powered with a little Samson Servo 120, I think the whole set up maybe cost me 500 bux. They're fun to mix on, and sometimes I even enjoy listening to music for pleasure through them.

The way I avoid needing a second pair is by treating my room, and mixing for 40 minutes or so at very very low volume, and for 20 minutes after that quite loud. Then break for 10. This cycle helps me keeping the perspective, enough not to need a second pair.

So.... to give you some background I come from an electronic audio background and I have over the years auditioned and built and owned tons of monitors. I also have had TONS of audiophile equipment very high end tube and solid state monblocks silver cables, all of the crazy items audiophiles drool over etc, etc, etc ....

Speaker design is crazy... you can take the same drivers and change the design and they are COMPLETELY different speakers. For example if you design with a passive crossover vs a active that makes monumental differences. The crossover slope and time aligned driver sounds completely different then electronically aligned phase. The box and corners matter... sealed vs ported are two totally different experiences and you can not have both. That being said speakers and the room you listen in are the most important thing we can do in our listening reference. Take Greg Wells as an example with his 60k PMC monitors he is currently using. To me it is fine to keep looking but do not loose your reference as you go or you will get lost quick if you do not know what each speaker is designed for. I personally DO NOT like soft dome tweeters, they lie and DO NOT reproduce accurately. I would rather have the truth even if it hurts.

I do think it's funny how us who record obsess 90% less over our listening environment and playback gear then people who casually listen and have NO idea what the original instrument in the room it was played in sounds like. So when you record next time think about the original performance and room.

I like to keep things consistent anymore, I know my monitors and I can hear well on them and they translate well. I would still like to upgrade but I am not looking.

As much as I am pro multiple monitors, your space is so small that I fear more baffles will cause more problems and it is going to be as much about finding something that works where you can put them as finding something you like but different.
Also your sub is really set up to match a single pair of speakers, if you want to set up the sub to work with both your going to make some serious compromises!

Got any phones? I really like my HD650's and AKG Q701's. Might be a good way for you to get a different perspective.

Apple Earbuds ¯\_(ツ)_/¯

Recently I've been testing my mixes with a Libratone Zipp (basically a bluetooth/wi-fi speaker - Sonos is the popular competition).  It's a common higher end portable (it's not "little") and a great mono test.  I'm thinking of getting another because you can then put them in stereo mode. The best part: I can test my mixes not just in different rooms or outdoors but in different locations in those rooms = basically letting me hear mixes the way people pipe music around their homes.

it is a parallax on the truth

you know it is the right move

unless you know your setup completely - with all its differences

4 monitor speakers? Are you recording in doubly now?

Apple just released a keynote for the $349 " HomePod " mono device 😂

"There’s also an A8 chip inside that does automatic EQ and echo cancellation with beamforming for the tweeters — it detects the size and shape of a room to tune the best sound."

"We built the high-excursion woofer with a custom amplifier to play a wide range of deep, rich bass. A powerful motor drives the diaphragm a full 20 mm — remarkable for a speaker this size. Meanwhile, HomePod uses an advanced algorithm that continuously analyzes the music and dynamically tunes the low frequencies for smooth, distortion‑free sound"

"HomePod has a unique array of seven beamforming tweeters that precisely focus the sound, from very narrow beams all the way to true, consistent 360º audio. By aiming those beams throughout the room, the tweeters create an immersive sense of space — no matter where HomePod is or where you’re sitting."

High-excursion woofer with custom amplifier
Array of seven horn-loaded tweeters, each with its own custom amplifier
Six-microphone array for far-field Siri and room sensing
Internal low-frequency calibration microphone for automatic bass correction
Direct and ambient audio beamforming
Transparent studio-level dynamic processing

I'm sort of in the same boat.  I do like  checking my mixes on the car stereo. Seems like I always pick up on what I'd like to polish versus what I'd like to eliminate or change that way, but only in a general sense. I think that maybe the benefit there is that I listen a little more passively in the car because I'm focused more on driving rather than the music itself ; if something pops up that I don't like I notice it more.
I have a VSP Labs power amp and some B&W CM5 speakers I've been toying with the idea of installing in the CR just to see if it inspires me at all, but I have to confess that I'm not sure if that's a can of worms I'd be happier keeping closed; it's too easy for me to over-analyze and second guess myself to death as it is.
For the moment it's not at the top of my list of things to do anyway- I'm finally installing a patch-bay and I'm betting that's gonna have me chasing my tail for the entire summer.