I mostly leave the sub on all the time but did compare briefly with it off. The Crown can make the RS5 do things in the midbass department that a SET amp can only dream of. With my SET the RS5 is pretty amazing but with the Crown the disparity between size and output is about double. It controls the cone motion better so IMD (intermodulation distortion) doesn't happen until higher volumes, another plus. Also, the transients are less compressed, which points out where the SET is clipping. Honestly, where the Crown really shines is at higher volumes, a small SET just can't come close. I tried my SET on a friend's Lamhorns, which have drivers 102.5 dB before horn loading, and it did not have the same limitations as it does on my Super 3 XRS, but there is likely a 9-12 dB gap in sensitivity between the two.
The other thing is if you mainly listen to vocal, acoustic, folk, etc. at moderate volumes a SET will be a better choice, it has a better midrange and at lower volumes the differences in power don't matter as much so the SET has an advantage. It would be nice to be able to just flip a switch between the two depending on what you're listening to.