Yes I would pickup Knox for this week, NO I would definitely not drop D. Williams. Underperforming, yes. Utter disappointment, very much so. You'd be really shooting your self in the foot though by dropping that caliber of a RB regardless of how bad he is doing. I own him too and bench him most weeks, however I wouldnt drop him for Knox or any other wire fodder.
You gotta stash him, Moore and Steve Smith are likely back this week, Smith next week at the latest. There is hope for Williams, don't drop him.
I'd drop Manning honestly. I would wait another day or so, in my league there is a Waiver lockout period of 2 days. I'd risk waiting on Knox until like Friday or saturday, ensuring that no other manager could pickup Eli for week 7. Then if you want him back after your bye-week blues, give knoxx back and snag eli on next week's waiver wire.
Start Colston, Harvin & Knoxx, driver is banged up and missed practice today.
Don't drop DeAngelo!