My current system

Paradigm Signature S4 -- Fronts
Paradigm C-4 center
Paradigm Monitor 5 Rear
Energy Es XL10 SUb
B&K REF 30 preamp
B&K 7570 Multi channel amp

In my current system right now my weakest link is the Subwoofer. I am planning to upgrade. I am planning to spend upto $1000 for a Second available in Audiogon.

My requirement 75% Two channel audio 25% Movies.


Which ones could match.

My questions are

1. Is it reliable to buy a used subwoofer thru Audiogon

2. It is not possible for me to audition the Sub with my system. Is that ok.

3. Which ones would be the best in my budget range.

Thanks
Pandu