You're operating under a few false premises: 1) that we could have had Marleau for a 1st round pick. 2) That Byron doesn't bring value 3) That we havent brought in similar players making similar money.
Sens will not hit the cap floor simply by re-signing guys.
Bryon doesn't bring 4 million dollars of value, that's part of why there's negative value in the contract.
It's possible that we would have never been offered a 1st for Marleau, but it wouldn't have been significantly less. It's not like Dubas has interest in overpaying for the Marleau buyout.
We're about 17 million away from the cap floor, we still need to sign Brady and Batherson (which would still only give us 10 forwards), we only have 3 dmen signed, and one goalie. I also wouldn't be surprised if we made a trade for a player that can be on LTIR or who has a salary significantly less than the cap. We're really not far from the floor.