I have upgraded my Magneplanar MG20 speakers with new caps from Janzen (silver/polypropylene) and Audyne (Copper foil). The inductors were replaced with Dueland 14 Ga flat copper air core design. This was done in steps with the caps first followed by Silver foil bypass caps from Dueland, then the inductors. The crossover wiring was with 14Ga. solid silver wire. Each of these steps were a solid improvement with the best area being in the imaging solidity and 3D quality of the soundfield. All the standard improvements in frequency (highs, mids, and lows) were there also. Then I replaced the cheap steel speaker terminals with WBT silver with another step improvement in the sonic character of the music reproduced by my system. Good fuses made a difference, but silver wire replacing the fuses was even better. I eventually took out the silver wire for SR Orange fuses because I shudder at the expense of shipping 7 foot tall speakers back for repair after I burn the midrange element out, damaged the bass panels, etc.
What I have found out once your system is revealing enough, everything matters to the reproduction of the music. Sometimes the change isn't what you were thinking about when you made it, but the change was audible. In my opinion, it is better to get speakers you really like, amps that match up with these speakers, power treatment for the system, and good cables first. What I did was speakers first, then preamp, amps, power treatment, cables, then crossover mods.
I have also added Dueland silver foil bypass caps on the amps and preamps, better fuses to all elements of my system.
I am a dedicated tinkerer, and really enjoy this kind of "tinkering" with my audiophile hobby. (even though most of my friends think, but don't say, you're nuts!) These guys spend their hard earned $'s on travel, which is also a good hobby also. I can't get them to come over to hear my system, which is disappointing, and not understood!