One problem with "top 4 RD" is that if a guy is unanimously considered a top 4 guy, he's got the price tag of a top 2 guy.
And then any of the "could be top 4 guys" also might not be but still have a high price tag. Look at the Samuelssons, Borgens of the world (not that I'd completely give up on either). Couple years ago they'd be considered solid middle pairing guys, someone you could pair with an offensive guy, and now they've got question marks.
There's a ton of variability in the performance you get from Dmen outside the top guys. Looking around the league at the top teams, there are some names that really aren't notable but are being contributors to successful teams.
I would take a swing on forward if our resources are limited and find any RD who won't let the play get behind them in transition.
Edit: The least popular part is I think Clifton could probably be fine in our top 4, which would just leave the bottom pair to figure out while Sammy is out, but in theory shouldnt be super hard.