For the Sprint device, check out the Sprint BuyBack program: https://secure.sprintbuyback.com/rbb/
You may be able to get a small credit on your account (not sure if the 8703e still has a value in this program).
They will also take devices back from any carrier for recycle, even though this program. Once you fill out the forms online, you then print out a postage-paid address label and ship the devices in to them.
If you cannot get a credit for your 8703e, and it's still in working condition, they may use it for Sprint Project Connect