To Trade or Not to Trade - RB advice

My current back in a 1/2ppr league are Martin, Murray, Gore, Williams, Mcfadden, Rod Smith. I only start 2 a week, and have not been getting much from Martin and Murray. I think I could get either Howard or Freeman if I trade both Martin and Murray, do you think I should keep rolling out Martin and Murray or go with either Howard/Freeman and stream a Gore/Williams/Dallas RB the rest of the way.

I would try to upgrade to Howard or push and see what you can get. Williams is a nice stream play if you need to.