Let's put your $$ to maximum potential.
How about option 3?
You can use a pre-fabricated/pre-finished cabinet($190) (textured black paint), sealed, 3 cubic foot, from
www.partsexpress.com and install an O Audio 500 Watt BASH amplifier ($230) and an Eclipse SW8200 driver ($230) in the cabinet.
It's not really DIY - unless you consider simply cutting the hole for the driver and amp as 'DIY'. If you actually wanted to go DIY, I can specify other options for this price range that will produce even more SPL and still have the same SQ.
What it is, is a substantially superior end product as compared to the SVS subs of the same total cost you are considering. The driver chosen is a TC Sounds engineered driver using their phenomenal LMT motor. It has incredible linear stroke of over 30mm. as verified by 3rd party Klippel Analysis. Compared to the PB12-NSD, you will get a little bit higher SPL (
and much higher SPL (50-60% more) if you use a larger amplifier; the 500W amp is not even close to using this driver's potential) and higher quality bass, unless you are considering the much higher priced PB12 Plus, in which case, I can recommend higher cost self-assembly options with higher performance and output for about the same price. The O Audio amp specified is critical due it's built in adjustable filters to compensate for the response curve in the sealed cabinet(
all sealed subwoofers use compensation filters, btw). The O Audio amp is also one of the best build quality plate amps for DIY use and it's even built in North America. The driver is well suited do a 1000 watt amplifier; but I'm specifying this 500W one to stay within budget of the SVS subs you listed.
-Chris