Received an email from Best Buy titled "Play like a champ with Xbox Live subscription savings". Inside there is a in-store coupon to save $20 on a 12 month or 24 month Xbox Live subscription.
Coupon states "Markdowns taken from sale prices. Not valid with any other coupons, offers or discounts" so this should stack with the $40 sale on a 1 year Xbox Live subscription starting 1/26.
Coupon valid 1/14/14 - 2/1/14.
Edit: It appears other users are receiving emails with similar titles but different coupon offers. YMMV on what you receive. Some emails offer the option to sign up for GCU for $60, others report a $20 savings offer for getting a DS4 controller & Knack.