dynaudio s5 vs c1 ?

Not aware of Dynaudio having a model S5(?)... but having owned the C2, I agree that they are very transparent, but benefit from having a subwoofer to fill out the low end and add fullness to the overall sound. The C4 on the other hand needs no subwoofer.

Are you comparing the contour S5.4 to the confidence series (C1 C2 C4)? If so yes the C1's and C2's don't have the bass punch that the S5.4's have. Have you demoed the sapphires or the new focus 360's? Both have a 'punchier' bass output. Personally I find the confidence series to be more transparent, better imaging and depth with more detail (timbre and air). That being said I own the C1's with a REL B3 sub and have demoed the C2's in my home (the C2's push the limit for my room). The C2's still could use the help of a sub but the C4's really don't need it.