Would be a mistake to pay up for Vanek as a rental IMO. Price is gonna be big and I bet he wants to at least see what offers he gets from other teams. Seems to have the same feel to it as Hamhuis/Garrison when they were pending UFA's and ended up signing with the Canucks, except Vanek will likely head to Minnesota with the cap going up and Heatley gone.
Burrows is no where near the fit Carter was for the twins, for everything Carter lacked (skating speed, defensive awareness) he fit the Sedins like a glove and currently two players I would love to see with them are Patric Hornqvist and also Eric Fehr. The reason these guys would make good fits is that they know where to go to score goals and are good shooters.
I've watched nearly every game both Carter and Burrows have played with the twins. and I'm sorry but if you think Carter was a better fit with them, I question your sanity.