I did the mods to the crossovers, midrange felt gasket, cabinet work (holes in mid compartment), superglue the cones, sprayed the backside of the mid horn with sound deadner, and replace foam surrounds.
I can say without a doubt it makes the speaker sound expensive, you have to hear for yourself because everyone has different likes. It does take more of a twist of the volume knob but the sound that comes out is remarkable.
I have compared them to stock 4024As, Klipsch KLF-10s, Klipsch Hereseys, The horns are much less in your face and very clear compared to stock.
I have always liked the Mach 1s for looks and for pounding out loud classic rock, so making them more refined and classy sounding has put a smile on my face.
As far as a kit to upgrade the crossovers, there isn't one but we have all the parts needed listed in the thread. I downloaded the info and have it in my computor.
I would put at least a 75 watt receiver or amp behind them, they like power and it makes them come alive. I have used my SX-950, and SX-1080 to test out mine.
I am also in the process of making aluminum plates for the plastic L-pads that crack and break along the screw holes.
