Contact your local DD dealer if you plan on purchasing new. If you don't want to go through a local dealer or there isn't one around you need to contact Digital Designs directly. Personally I'd look for a good deal on some used or reconed DDs since they're pretty expensive.
Those 2 dc sounds lvl 4 xls 10's did a 149.1 for an spl burp in a daily box and in the 148's on music with a 30 second average if you call that not as good. And they will have clean lows unlike the dd 9500. This was in a 04-05 vw golf. Get a dc sounds sub of this series in the 12 or 15 and be just as good as that dd 9500 but with cleaner sound.