Universally good(quality, build, accuracy of output with minimal distortion) and a flavor of sound that suits your personal taste are two different things. Sometimes it's better to suit your personal tastes than to get the all-out best designed driver.
Yay at the Audiobahn reference(Swiss),
Fi Q works in a relatively small box, offers lots of excursion for sealed and gets low ported.
Polk Sr needs a relatively large box, has limited excursion to work with, gets very low ported, geared for lower power but similar sensitivity as the Fi so same output anyways.
Boston G5 again needs a somewhat large box, also has limited excursion, nearly identical low frequency response as the Fi Q, a little louder than the Fi off the same power(2dB), high qms which I'm a fan of.
Just from specs and modeling them up, I'd lean towards the Fi Q. There's more capability there, and you really don't gain much of anything with the other woofers. The Boston will be the most transparent/quick though if you're looking for the most musical.