Use of the amorphous core in the RAAL tweeter takes micro-dynamics up a notch. It's akin to lowering the noise floor, you'll get a bit better center image focus and better definition of tiny detail. Even with the standard core the RAAL might have more micro-dynamics than any tweeter I've ever heard, with the amorphous core it's just spooky how delicate and detailed it can sound.
The crossover options offered are Teflon V-Caps as bypass, Clarity Cap MR throughout the crossover, and Mundorf Silver/Gold/Oil. The standard crossover caps are good, that's what we showed at RMAF with V-Caps on the tweeter circuit only. Both the Clarity Cap and Mundorf options are if you want the best, and while the improvement is small, it is there. The Clarity Cap is if you want completely uncolored and neutral, the Mundorf gives a bit more of a lush sound with some warmth and musicality.
The primary characteristics I'd say of the Cirrus are absolute see-through transparency, and a fast - detailed - uncolored sound.