Eric,
The biggest part of Stan's mod is a redesign of the discrete output stage. This is the part which takes the DAC's output, buffers it, and also has a low pass filter. You can set the filter to 40 or 50 KHZ.
Stan adds at least one transistor and a diode (I think), and changes values of other resistors. He also add's blackgates to the DAC/output board, if you want, and to the power supply.
Dan has his own mod, where he completely bypasses the existing output stage, and puts in his own. Based on his rep, I am sure Dan's mod sounds good too, but it more expensive too.
That's the trade off with Stan, he has a big backlog, so it takes a long time to get something modded by him, but he does good work, and his prices are cheap.
I never heard the 1000 stock, so I am not sure how much Stan's mod did for it. I am going to mod my 1000 soon, so the LR sides will output LR front information. These stages were not modded, so then I will be able to compare the stock output stage to Stan's output stage.
I am also going to try an transformer output stage, and see how that compares to Stan's output, but that is a few weeks away.
Randy