I'm not sure GS is that much better with him. Even with the new cap they will have to give up a lot to pay those 4, even more in the next season or two. Looney, Iguodala and Livingston are under contract and likely stay...but the rest of the roster will turnover and I'm not sure that 7 is enough.
They will have to sign some serious scrubs to fill out that roster over the next couple seasons...and its because of the same cap that made this foursome possible...with the new cap who wants to sign a mid level exception or minimum deal when every average player and career backup are getting huge deals handed to them....this is the season to get paid, not chase a ring...and next year will be more of the same as the cap grows and they have to max out Curry and Durant at $200 mil each.
Durant is a better offensive weapon than Barnes, sure ... but defensively and rebounding this team will be much weaker... they are not going to have any proven size. I don't think 70+ wins or a title is guaranteed to them, not at all... In fact KD's inability to close out playoff games is why OKC failed...and it will be more difficult to fill that roster out than people are thinking about.
http://www.basketball-reference.com/contracts/GSW.html