I've been after a subwoofer for awhile to go with my Q2020i's and receiver. An online retailer currently has the Wharfedale Diamond SW-150 for £160 with a two year warranty. Someone local to me is selling one second hand for £100 in good condition. Is it worth paying the extra £60 for a full warranty and peace of mind? If I do go and take a look at the one for sale local to me, I will be asking for a demo before handing any money over but would there be anything specifically to look out for? I'm not sure how old the sub is, but they are selling due to an upgrade.