if you're looking for a solid spl woofer, the 1506 is a good choice. not only is it the most asthetically pleasing sub i've ever seen, but it will take just about all the power you can give it and come back for seconds. The sound quality is a matter of taste. If you're accustomed to audiobahns and other SPL woofers, this will sound really awesome in the SQ department, but if you're of a more descerning taste, it will probably won't sound that great. Bottom line, if you want massive SPL and great looks and are willing to sacrafice some SQ to get it, this is your sub.
Also, check out the 1508....a little priceier, but worth it IMO.