The RSD12" was rated top 5 out of all the other subs CA&E tested, and the subs above it were all priced 500$-2000$.
Let me see if I can find the link...(Not that this is proof of anything, other than the opinion of the article writers and is limited to the subs they decided to review).
http://www.caraudiomag.com/service/caep_0610_subwoofers_buyers_guide/top_10.html
TOP 10 REVIEWED SUBS
1. Critical Mass UL 12 91
2. Alpine SWX-1242D 88
3. Cerwin-Vega Stroker Pro 15 88
4. Phoenix Gold RSD12 86
5. Earthquake Subzero-12 82
6. Xtant X2.1044 81
7. Rockford Fosgate P212S4 79
8. JL Audio 10W6v2-D4* 65
9. Rockford Fosgate T210D4* 65
10. Image Dynamics IDMax 10D4 V.4* 64
Digital Designs 3510d* 64