But don't you compromise the sound and balance andrew achieved though?
The short answer is "no".
In the $76 dollar upgrade nothing about the original design is changed except for one by-pass cap being added across the resistor on the tweeter circuit to lift up the rolled off top end. This corrects an amplitude problem (rolled off top end) and restores spacial cues in the top octave that effect the imaging and sound stage layering.
A capacitor in the tweeter circuit is upgraded to a Sonicap, but the value is not changed. And the resistor is upgraded from a sand caste resistor to a Mills resistor, but the value is not changed. Both of those improve clarity considerably, but they do not alter anything else.
And a sheet of No Rez damps out the resonances of the un-braced 1/2" thick cabinet material. So the bass is cleaner and more controlled, and the lower vocal region is cleaner from this as well.
So the level 1 mod makes improvements across the board without altering anything about the design.
The level 2 mod changes a few things that are what I'd call small issues, but improves all the crossover parts, wire, and connectors as well.