Well I finally managed to get the subwoofer installed in my friends truck. My first impressions of the SAv3 are very, very positive. It digs extremely low for an eight and makes it look effortless. Its rated for 500rms and is currently taking 800rms and enjoying every little bit of it. Although I only got about 30 mins of listening time in, the Sundown absolutely impressed us. Lots of output, easily plays to 30 flat and probably in the 27-28 range before falling off. Very well built and easily the best 8 inch sub I've ever heard. Musically and output wise. My experience with Sundown is minimal and I've only owned a couple of 8's myself (massive hippo, and another brand that completely escapes my memory) but I would surely recommend this sub for a wide range of applications.
I'm officially a fan of Sundown now.