I haven't heard any of the other subs although I have read a considerable amount about SVS. From what I have read, the 500 appears to be a more "musical" sub than SVS while doing double-duty for movies. This is very important because not only do you want a sub that's going to reach deep and loud for movie effects, you also want a sub that's going to be articulate and transparent for music.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated