Regarding the stock mini-plug version from Sound Professionals (853/943/933)
I have had significant distortion with the AT943(bodies)/AT-ADAPT/853(capsules). I also had significant distortion with the 943 with microline capsules. I experienced significant improvement in my recordings when using the 4.7k modification.
I have noticed that the 853 distorts sooner, but in my expereince with about 10 pairs of AT's, the 4.7k and 2.2k will help the recordings. I think even if you are not having distortion problems the lower sensitivity that this mod provides will keep the rest of your signal chain from overloading in loud situations. Lets face it, people are not using professional preamps like the grace or apogee boxes with these mics. Also, having a 4k2 or 2k2 in there better mimics the 3wire powering of the typical configuration of these mics.
Now, knowing a little bit about why Sound Professionals decided to offer this 4.7k/low sensitivity/Church mod, I can agree with Church that they are not testing the distortion before and after in any scientific way. I can say there is real world results showing the benefit in sound to either 853 or 943.
I certainly don't have the credentials that Mr. Church does and I respect his work, but I have seen the benefits from the 4.7k mod on my 943 mics, so I disagree on this topic.
Now, I will be willing to blindly agree with Mr. Church on any topic here, if he gets the "Church Transformer Preamp" done in the next few months.....