Nice review. I also like Paradigm and came close to getting a set of Paradigm Reference speakers quite a few years back. But, really, for the money I was going to spend (before the B&M store went under) my Salk HT2-TLs are in an entirely different league with regards to detail and clarity. However, I never heard the Be tweeter, so who knows?
Anyhow, if you were looking at moving up to the S2 bookshelves at a similar price to the ST-RTs, why not audition a pair of HT1s with the G2 ribbon tweeter and stick with bookshelves? Besides, I'd love to know what you thought of them compared to the S1/S2s.