As far as immediate impact, I think Wallace, Watson & Weddle will be huge this season. Watson is a good RZ target, but Wallace gives back that speed which Torrey took to SF. If Perriman ever gets on the field, the combo of having to cover both Wallace and Perriman would be pretty daunting. However, just having Wallace is a big step up, if only for speed reasons.
Weddle will change everything for this D. He's smart, quick, but maybe most importantly, he's showing that leadership gap we've been missing since 52/20 left.
I think Young and Moore also see time and make an impact as the season progresses. I'm a big fan of the KC pick, love that he's being a menace already.