I would have to agree, you need to get a QB. Its imperative. I would say if you go 2 QBs, Roethlisberger is the lock for your Favre replacement, and follow it up with Manning or Rivers who will help immediately whichever you prefer.
However, I can't justify passing on Greg Jones at this point. As currently a possible goalline back, and a future prospect to take over for "Fragile Freddy" he's got potential to be a full time starter in a year or 2. He's at least as good as Buckhalter going into this year, and bolstering your RB core is something I just wouldn't pass on.