I own a Velodyne SPL-1200II, two SVS 16-46PC+ subs, helped install a Hsu STF-2, and also have two DIY subs. If you want the most bang for your buck without building your own, get the SVS. There's no doubt in my mind. The Hsu subs (Hsu also designed the Outlaw LFM subs) are also good values, but there are more options and better looks from SVS.
Keep in mind that the roll off is different between sealed and ported subs. And most of the SVS subs are ported. Within the same volume enclosure, a ported sub will reach lower than the sealed subwoofer unless the sub's amp comes with a boost. The trade off tends to be less volume in the upper frequencies. But where as a sealed subwoofer will have some output below its F3 point, a ported subwoofer won't.
Example: 16-46PC+ tuned at 12Hz has SPL at 10Hz but absolutely nothing below that. SPL-1200II has an F3 of 22Hz (IIRC) but has some output below there which room gain can help with, if your room suits.
The reason some people say sealed subs are more "musical" is because group delay increases as you approach a port tune faster than it does in a sealed sub. But that's not a universal truth and sometimes the ported design will have lower group delay than the sealed design.
