I will simply reply that the SX10 is not the same thing, sorry. The Icon motor is machined here in the USA with spiral axis cooling with USA steel. The SX cannot remotely say that. That alone is more than enough difference as to why the Icon costs more and is the better choice. RE is a cheaply built overseas copy of what it used to be. Now if you said original Icon from 2007 and old special order USA made RE SX Hybrid, then you are closer.BUT!!!! That is off topic, back to the originally asked X10 / SA-8's on the same power. As I have not heard them head to head, it is difficult to give an experienced reply, doubt many outside of the Sundown HQ has tested the SA-8 head to head on the X10 since the X series is so new. Anyway, all things equal in proper enclosures, I personally will pick the option of more cone area and less power compression, meaning in this case the pair of SA-8's. Because even though the coil in the SA is smaller than the coil in the X, it is still the combined coil surface and cooling of the motors, and even though an X10 has more area than a single SA8, the pair of SA8's combined have more swept cone area. So to stay on topic and give an educated guess on the initial question at hand, I would lean towards the SA-8's.