It's the wrong time of year to sell an entry level deer rifle. Anywhere.
And dealers, all dealers, base the value on their wholesale price and how fast they think they can sell it.
.308 calibre deer rifles do not sell well in March.
The SPS is not an expensive gun so I don't think you'll get a lot for it. You'll get raped at Gander for sure. You need to sell it on your own to get anything for it.