The PB-1000 will dig deeper, but the DSW660 will have more output above 30hz. I would probably go with 3 outlet PB-1000's for the 20hz extension alone. That is the difference you will see between ID and Brick and Mortar subs. ID(Internet Direct) usually will provide deeper bass extension, lower distortion, for less money. the reason being is the middle man is cut out of the equation. One thing you will also notice is the standard box brand subs are smaller then ID. Smaller subs are usually more attractive to the average enthusiast and sell better due to WAF. the problem is they are harder to tune deeper due to the inability to increase the port length enough. Some companies employ a passive radiator to increase bass extension but that drives the price up and now you are at the price levels of the DSW Micro pro series, which are gawd awful expensive for what they are. This is a prime example why ID subs are larger...Larger enclosures increase efficiency, allow deeper tuning, and require less power to get good output. It's a win win if you have the room for them. Like the old saying goes, there is no replacement for displacement. Imo Enclosure size is far more important then driver size alone.