Comparing S2K retros to Mini H1s?

That's like comparing BluRays to DVDs.
In cost alone, there is no comparison. At about $200 for just the projectors with the clear lens, the S2K's width and output had better outperform the Mini H1, which run for $125.
Performance-wise, the S2K is, without a doubt, the better performer. The width of the beam is wider (though I'm sure it's not twice as wide, that seems like a stretch) and there is a more visibly concentrated beam toward the center. This is due to how the projector sits in relation to the trim in the headlight. I'm sure the S2K has the better cutoff in both color and sharpness as well. Let's not forget though, the Mini H1s are bi-xenon, while the S2Ks are not.
Btw, this is far from an "intermediary upgrade."
S2K > Mini H1 > TSX > HID PnP kit
Are you saying that the TSX retro isn't a real retrofit?
EDIT: I just re-read your post. I think I might be misunderstanding what an HID "retrokit" is. I originally thought you meant plug and play kit, but I'm guessing you meant something different?