Motorola SB6121 DOCSIS 3.0 Cable Modem $34.40 - Staples B&M Clearance YMMV
Even if you already have one, it's a good idea to have a backup. Cable modems do go bad, and if you need one in a hurry they can be expensive.
1) sign up to get $10 off $50 coupon here: www.staples.com/emaildeal
2) get 20% coupon here: www.staples.com/coupons
The coupons WILL stack even though the fine print says you can't combine coupons. Better hurry if you want this deal. This is a clearance item and my local Staples store only had 1 left.