It's nice to rosterbait and all, but I think we are thinking about this the wrong way. It's not just about "how much better can we make our team" it's about, is that team going to beat the Penguins. Is this team fast enough AND skilled enough to beat the Penguins, because right now I am not seeing that roster.
Realistically, any roster that includes Joe Thornton, Joe Pavelski, and Logan Couture as half of the top 6 is not, in my opinion, going to have a chance. We got our ***** handed to us, we were damn lucky to even get it to 6 games. Primarily because they literally skated around us like we were standing still.
If it were me, I would cut bait at this point. Let Joe walk, trade Pavelski to a team needing a character guy with high skill, and bring in skilled high speed top-6 guys. Sure, losing our #1 center is a death sentence as well, but we are losing him either way, and spending a bunch of assets to build a great team that still loses to the Penguins really doesn't do much for me.