Subwoofer match for Vandersteen 3A sigs?

Has anyone used a subwoofer other than Vandersteen with the 3A signatures with good results? Recommendations please.
Why would you want to?
Why.. mess it up
Go to You'll find a free issue (#2) dealing with adding a susbwoofer - specifically to the 3A. Hardesty seems tothink there are a lot of reason to add a subwoofer. I might do so myself, as I too am debating the addition.