Different tools for different jobs. I'm not an expert on playback either.
For me:
Party = the Mission 5 towers
-loud, colored, but enjoyable enough. I'm probably moving on from them soon.
For Summer it's a pair of deck speakers and on a clear day, I drag out a small sub.
Any critical listening is done on headphones, and on an old pair of monitors then, in my house and car.
I'm not good enough to trust my ears and only one set of speakers.
When I thought that I had a perfect EQ of a recent show, I played it in the car and it sounded like ass.
Back to the drawing board. I am learning how to shape the bottom end. That seems to be where all my problems stem from.
Room treatments have helped alot.
One thing that I've noticed about an excellent master, like DSOTM, Trey Album, new Sam Bush, Steeley Dan, Allison Krauss, etc.
No matter where I play it, it always sounds good. Even on a boombox it is as good as the playback system.
A bad eq will fail somewhere and show it's evil side.