Thanks! I get the impression that SYLVER/SAMPSON with ASTER-30 and ASTER-15 are designed for extremely long range and high altitude anti air defence. What I really want for the cruisers is something that will just be able to handle aerial threats that threaten the ship and those in it's immediate vicinity. The key role of the cruisers is to launch supersonic anti ship missiles.
The kinematics of the ASTER missiles are such that they offer long range point defense, but not area defense. I'm going to edit this post later when I am on a real keyboard.
Ok: the APAR System is designed for non-active seeker missiles such as ESSM, NSSM, and the Standard series. The ASTER series is a series of active missiles (they do not require a radar beam to be sent from the ship for terminal homing). You've used the SAMPSON radars across the rest of your fleet so for standardization, and systems compatibility, it would make sense to keep using SAMPSON. As for SYLVER vs Mk-41, it really doesn't matter so long as you can fit the missile in the cell. The larger cell in the Mk-41 lets you fire a larger missile (such as the Standard Family, VL ASROC, or Tomahawk).