they sound better and have a higher SPL handling ability running them 3-wire/the AT power boxes/another box with the phantom power adaptors/custom made 3-wire BB vs 2-wire (terminated into a single mini plug) thats why they "clip" when running them off a battery box/plug in power while in loud situations. They were not designed to operate like that.. Soundpros sells them like that as a (lower price) standard package vs. selling them as they are made (mini xlr) then having to sell the adaptors and a phantom power supply/custom made 3-wire BB which is obviously a much higher cost. They do/did offer the "high SPL mod" (which is simply putting the connectors back on that they took off) and a pair of adaptors..but, in reality this isn't a mod, this is how they come from the factory.. the single mini-plug termination is the mod (which doesn't work well)
The high SPL mod is another matter completely. I think that's the Chris Chruch mod that adds a resistor somewhere - that mod was later revealed by Chris and then summarily copied by SP...its more than just a connector swap.
Soundpros original "high SPL mod" was putting the xlr connectors back on and including a pair of Nady or AT phantom power adaptors. The resistor mod was brought in by Chris Church afterwards. I bought mine around 8-9 years ago..so.. I'm sure they have changed their website as far as the options for the mics. Regardless, 3-wire is the correct way. The resistor mod makes them close to the SPL handling as the 3-wire, but they have slightly higher noise than.
(they even had yet another HIGHER SPL option, but that was just including a set of the AT power modules (one per mic).. they have mini xlrs in. I had a pair of the 8532s at one time, but they made the mics sound very flat)