Deal: Grab an iPhone 6s for $100 off and get a $100 Amazon eGift Card
But you're going for a brand new phone, Amazon has a decent offer available although you'll have to make some compromises. Usually selling for $300, the iPhone 6s (32GB) is now available at Amazon for $100 off.
The main downside is that it's locked to Simple Mobile, so you'll have to activate a new line of service by May 31 on the carrier's website. On the bright side, a minimum 2 months activation is required, so you won't be tied to Simple Mobile for too long if you don't want to.
Another benefit is that you'll receive a $100 Amazon eGift Card when you buy the iPhone 6s. The card will be sent to you within 7-14 days of second month of activated service (while supplies last). Obviously, you'll receive a Simple Mobile SIM kit when you purchase the iPhone 6s, so you don't have to worry about that.