On SVS website is says...
What is the warranty period on my new SVS product?
SVS has a 5-year bumper-to-bumper warranty, which is one of the longest and most comprehensive in the consumer electronics industry. Warranty exclusions include (but are not necessarily limited to) force majeure, acts of nature, AC power surges, and abuse.
So as long as that sub is less than 5 years old, you're set ..... but as everyone has already said, make sure that it is in 100% working condition. Make the guy put it in writing if you have to.