you must order them from an authorized dealer. there is one in my town you could call to get a MUCH better price, but you would probably pay an arm and a leg for shipping. lol
Treo SSX 12" retails for around $700 Treo SSX 15" retails for around $900 Treo SSX 18" retails for around $1000
Treo CSX 10" retails for around $650 Treo CSX 12" retails for around $750 Treo CSX 15" retails for around $900 Treo CSX 18" retails for around $1000
the SSi do nicely as well,they actually have quite a bit of SQ to them, and they cost about half as much as the SSX's. they handle 750wRMS(which is plenty LOUD) on the 10",12" & 15", and 1,000wRMS on the 18".
Treo SSi 10" around $300 Treo SSi 12" around $350 Treo SSi 15" around $400 Treo SSi 18" around $450-500
again, you can get them cheaper at an authorized dealer, they are kinda pricey, but well worth it and they come with a three-year dealer installed, 90-day purchase warranty(not installed by authorized dealer)
they are at the same level with DD in my opinion, i currently am using a Digital Designs 2000a 10" sub right now and havent had any problems with it and i play it loud every day, and have had it for well over a year now.