Duramax - indeed the connector is paramount to performance. I've taken a very deep dive into signal propagation, and know there is much confusion and lack of insight in the arena. The wire guys have paid good attention to metal purity and dielectric characteristics, but still haven't settled on a 'best' geometry. I continue to investigate that aspect (with some tangible success). What seems to be nearly ignored is the termination which plays a huge part in proper propagation through the signal chain.
Consider the signal path as like a water-slide. As an example, consider the end of the slide to meet a spade connector. Smooth flow turns to whitewater. Independent of metal purity, gauge/ampacity/ etc.the turbulence has significant negative effects. I am not overstating, and you are correct that listeners would be astonished.
For practical considerations I want to disconnect the amp and the speaker. Presuming an outboard crossover, we can attach the input and output pigtails to the crossover and have good user interface. At the amp end I strongly recommend locking banana plugs due to their inline arrangement of field propagation. Of course your idea of direct solder connections could be better. But I posit that the geometry of that soldered connection is critical. Axial, left-lay twist is the correct way.
At the outboard XO we can manage inputs from one or multiple amps with inline soldered connections. Same on the output. Note that I had some custom bolts made in 6-9s copper which I have now abandoned due to the propagation disturbances we are discussing here. I replaced those with thin-wall copper tubing with wires fed into each end, touching in the middle and soldered at the entries. That out-performs any post I have tried. GR's Electra takes that idea up a few notches with purer copper, thinner walls, and the convenience of unplugging.
Note that solder per se is not an ultimate solution. Heat disrupts the molecular structure and metals dis-similarity is less than perfect. In summary, I consider the roughly $12 / connection to be funds well spent.
Note that the 2.4 is electrically a two-way; the mid to tweeter crossover is visco-elastic / mechanical. So we'll need two pairs per channel which will cost around $50 / channel. That's a lot more than nothing, but less than one typical upgraded capacitor. The proof will be in the listening, but there is a lot to like here.
For your straight-through solder proposal, you might consider the copper tubing idea at the speaker inputs. I plan to re-fit my amps with Electra outputs.
