Smith is a definite upgrade over Brown (although I like Brown's future). Could you sell a trade for Boldin instead? He's struggling but his name alone might do the trick. I'd just be a bit worried because Jennings and Boldin are both down a bit and if they don't return to form you could seriously miss a guy like Smith.
I don't think S Smith will keep up this pace, so it is a good time to sell high. I just worry about where your WR corps would be after that.
If you feel confident in Jennings and Boldin, then go for it. K Smith is legit. But if you have questions about your WRs you might hang on to Steve.
Good luck, and please see mine:viewtopic.php?t=454516