Thought I'd put some refurbished links to places, since their inventory always changes and you can keep tabs on stuff.
Adorama doesn't seem to post email link specials like before. The key is search open box, then narrow down the category, like this one for headphones.
Shop Used Open Box Deals on Headphones & Earphones by Earphones & Earbuds, DJ & Studio Headphones, Wireless Headphones, Wired Headphones & more. From brands - Sony, Apple, Focal, Westone, HiFiMan, Sennheiser, Bose, Turnstile Audio.
www.adorama.com
Amazon Renewed is hit or miss, better discounts than the warehouse, but I couldn't find this link off the main menu.
Creative Labs has a renewed page with a 3 month warranty on their stuff. Prices have gone up on some things like the Soundblaster G6 though.
All refurbished products come with a 90-day limited hardware warranty.
us.creative.com
Sennheiser has a renewed page also, and 10 percent off first purchase if you sign up for the newsletter. With the number of fake ear buds (the giveaway is the box, looks like it was printed on a laser printer), it's the only place I'd buy those used.
Discover certified refurbished products at reduced prices - tested, checked, and thoroughly inspected to meet the same high-quality standards as our new products.
www.sennheiser-hearing.com
Drop Refurbished has been a little slow lately, I think they update on Fridays like their sale page.
Repaired, restored, and extensively tested, our refurbished products carry the Drop standard of quality. Shop top exclusives in Mechanical Keyboards...
drop.com
Rtings has a resale page for all the things they review. It's nice since they link to the review they did to research it.
www.laboratoirertings.com
Schiit has a B stock page as well
www.schiit.com
Woot.com has some cool things at times, but I use Wootsearch since on Woot there's no search box. Not linking direct since they do some affiliate thing. Can always just open a new windows in Woot if you find something. I'm not a fan of affiliate marketing since credibility on a review goes right out the window when it ends in a buy it now link.
https://picclick.com/ is a good tool, since they show a LOT more information on a listing than even eBay does with an advanced search.
Also
https://camelcamelcamel.com/ is good for tracking Amazon prices if you buy used, or especially before black Friday or some known sale. Just have to set the threshold for price pretty low or the emails get annoying. On Amazon always use a web browser, since the phone app doesn't show their lowest prices for stuff like a used version being offered. For eBay it's the opposite, set alerts on the phone app so you'll know the second a new item comes up for sale. The email alerts are useless since they get sent at 9am PST and anything really good will have been snapped up by then.