I don't understand the hesitation around here on getting Anthony. Even if he's not a superstar, just a scorer, not a good defender, passer etc. his track record speaks for itself. He has been in the playoffs every year as the number one option on his team. There are only a few guys in the league with that kind of talent, however you may feel about his attitude and playing style.
This reminds me of the Bulls a few years ago not wanting to let go of guys like Deng and Gordon in trades for Gasol or Kobe (if the trade rumors were actually true). At that point they thought they had an upcoming young team, and put way too much value on guys who had serious flaws in their game, and expected all the young guys on the team to develop and correct those flaws. Fast forward a couple years, Deng never learned to shoot the 3 and create for himself, Gordon developed any PG skills and became a bit of a chucker, Tyson Chandler never reached the ceiling they had projected, Curry got fat and fell apart (funny that he is the only one from that era who they actually got any value for). Hinrich just kinda sucked. Now Deng is on a horrible contract, Chandler, Hinrich and Gordon are all gone with nothing to show for it, and they fell back into the basement.
On the other hand, look at what Riley did with the Heat. They had a great young trio with Wade, Butler, and Odom, and huge momentum after Wade's rookie year, plus some good roleplayers, but instead of falling in love with a good, but not great bunch of guys, he cashed in on the value they had built, and parlayed in into a championship. Not saying that Carmelo is anywhere near Shaq, but the great teams go as far as their best players can take them. Boston is another example of this working out.
So in my opinion, if you can get Carmelo while still holding on to Cousins and Evans, even if you have to gut the rest of the team, then you do it. Fill in the roleplayers later, try to hold onto the best defenders out of the young guys, ala Boston, guys like Casspi, Landry, Thompson, Garcia, Beno, and Whiteside can all be replaced.
With all that said, if the Maloofs are serious about bringing in Carmelo, it shouldn't take gutting the team to do it. With our cap space, and maybe bringing in a third team -sending Billups to Atlanta for Crawford's expiring and sweetener from us if needed, for example- Denver can come out of this deal saving upwards of 30 million dollars this year,
getting some young guys and picks, and having huge capspace next year. Basically kickstarting a rebuild in one move.