I have not heard the Vienne or the Triangle, but having heard the other three, I can affirm that Paradigm just is not in the same league as Thiel or ProAc (or even NHT and many other brands). Their reall small speakers are quite impressive for the money, but the larger models just don't do it for me. I just helped a friend pick out a system, and we auditioned several models in both the Monitor and Studio series from Paradigm, and not one of them could compare to the $1,000 NHT ST-4's (which are stupid good, for the money). My friend went with Totem Arro's, BTW. The NHT's were probably his first choice, sonically, but the Arro's also sound darn good, and have incredible WAF ratings!
Getting back to Thiel or ProAc, I have a hard time deciding which brand I prefer, and those are my two favorits in dynamic speakers, BTW. I have Thiels at home and ProAc in the office. They each have their own sound, so it'll come down to personal preference, but I think that you would be well served by either the CS2.3's or the D15's.