Generally a subwoofer operates up to between 50 -140 hz. Above 100hz it will become directional so a single sub tends to cause problems. Manufacturers run their subs too high because their small satellites don't go low enough to meet the sub and really need woofers not a sub woofer. This causes a suck out in the bass that a sub cannot fix.
The Paradigm is good. Most subs have a boomy quality caused by a design choice that makes the sub sound louder but really screws up the sound badly. With the PS-1000 you can use some foam to plug the port. This may offer tighter bass with more definition depending on the room.
If your room is not big a smaller speaker in the sub may be better. If your budget were higher a new Paradigm sub with their optional PBK room correction kit would be great.