well, there is a sticky "What speakers did you replace" that may be useful.
Speaking of paradigm, I have auditioned the ST and S6 at my home, these two were pretty comparable. The S6's have larger woofers and can move more air. They did not go deeper, though. But, providing that they cost 4.5K or more, it would be an easy choice.
I doubt that the S2 and the ST are in the same league.