Because of the power limitations of the E-530 amp and because of the large dynamic variation in classical music I would not recommend you to get the S5.4s. Firstly, the amp will work much harder and therefore will get much hotter when driving the S5.4s. Secondly, from my experiences, you will not be able to achieve that much higher SLP levels with the S5.4s compared to the S1.4s before the amp will clip. If, however, the S5.4s appeal to you that much, try them in your room before committing (and check the meters of your E-530 amp).
On the other hand, I second the C1 + sub(s) suggestion(s). The C1s alone would be a significant step up from the S1.4. Adding also a good sub (e.g. Rel or Velodyne) will further improve the playback at both loud and soft volumes. Normally, clipping should not be a problem in this set up. I too have an Accuphase combo, the E-550 class A integrated (like yours 30 watts into 8 ohms) and the DP-500 cd player driving a pair of Focal Micro Utopia Be complemented with a Rel Stentor 3 subwoofer. In the dealers room, the E-550 clipped while driving my Micros (without the sub) at loud levels. This however never happened in my room where I also use the Rel (even though my room is approximately two times larger than the dealer's room).
For classical music and piano my speaker recommendation would be Avantgarde Uno or Duo. I have recently listen to the Unos driven by the Accuphase E-560 class A amp and the combination was just marvelous. Due to their high efficiency these speakers are able to give a rather realistic reproduction of the dynamics of an orchestra at both low and high volumes, plus the 30 watts of your Accuphase will never be an issue.
I have never heard the Jeff Rowland Continuum 500 integrated, but being very found of Accuphase I would recommend you to go for one of the more powerful Accuphase class A/B integrated, e.g. E-408, E-450, E-460. You already like/know the Accuphase house sound.