Acceptable Speaker Combined SPL Ranges

I have just started on my speaker design journey and have very green question, I couldn't locate any existing threads that seemed to cover this so apologies if they do exist.

I understand a flat combined SPL response is the ideal loudspeaker design -- but in the real world what kind of bounds would be considered decent/good/excellent?
For example over a range of 50Hz to 20kHz would +/- 1dB be excellent, +/- 3dB be good and +/- 5dB be decent?

I've just started doing some modelling of different crossover/driver combinations using VituixCAD2.

I was a little surprised when one of the best looking results I've found so far was an unusual crossover configuration (3way 2nd order series) with cheapish drivers. The combined SPL stays between 85-90dB from 60Hz through to 10kHz, with a spike to 94dB at the subs resonant frequency (~42Hz) and gradually increasing slope to 93dB as the tweeter goes off the end of the scale. I then realised that I have no idea if this is actually a descent result or if all my other results using much more expensive drivers and more traditional crossover designs were just worse.


I've just started so this is without fine tuning the crossover and with cheaper drivers that do not feature smooth responses so I expect improvements could still be made (likely with a price tag) or just tuning the amplifier equalizer to dampen the high and low ends. I also don't know enough to tell if there might be detrimental phase/delay issues with the design, but that can be the next hill to climb.