When I started to play saxophone again after a 25+ year hiatus I started looking for ensembles to perform with. I started with a community band to find connections into the local music scene. I really love big bands but found that most played the same old music, and it became rather boring. So I created my own, 20 years later called the Seattle Solid Gold Big Band. I also started a sax quartet called the Dissonance, now called the Seattle Solid Gold Sax Quartet. Check out their many ensembles here: https://seattlesolidgold.com/
The nice thing about starting a sax quartet is that I get to pick the music. I can select pieces that take advantage of our strongest players. I can pick music that I adore. Also, it is so much easier and fun to pick the performers who will stay with the ensemble for more than one season. During the 20 years of my sax quartet there have been a *lot* of musicians sit in.
Developing a book of favorite charts as taken some time but my tenor player Gary has helped me tweak our listings with charts he has arranged and/or penned. I now have a rather nice list of charts to select from for almost any performance and venue.
The best part about playing in a quartet is that every musician is soloing the whole time, there is no place to hide like there is in a community band or big band. So you get to work on your fluidity and sound in an almost perfect solo-like setting.
I now recommend this method of finding groups to play with to my musician friends with some management skillz. YMMV.
The Bis Key Chronicles 
A quartet is such a great idea. I agree that small group playing makes us better musicians.
Jim Collins