It is important to note that the budget is not really defined by the salary cap, since Danny is not likely to go under that.
The budget will more likely be defined by the luxury tax threshold, which after next year will likely be around 76-78-ish million or so.
I've gone through the math in detail elsewhere and assuming you start with bringing Asik & Lin over in the infamous TPE & non-guaranteed contracts (Bogans, Babb) deal to help Houston clear space, let Bradley go, then get Love for draft pick value, one of our two young PFs and expirings (Bass, Anthony) and there is probably room for re-signing Rondo, Asik & Love each via Bird rights next Summer and still stay under the LT 'hard' cap. The following year Wallace comes off the books so you can afford to raises for Green & whichever of our young PFs we kept. You'll need to get a stud SG out of the draft with the pick we keep in order to replace Bradley.
So, you can make it all work. There is no Carmelo in this scenario, though, and no room in the budget for him (or a similarly priced player) unless, say, you trade Green & Wallace' contract space, maybe next year, for someone. I haven't looked yet to see who might be available.
Absent such a deal, you'd be looking to try to contend with Rondo, young SG stud, Green, Love & Asik as your starters with a maturing Sully/Olynyk (whichever you kept) as your 6th man.
I'd rate that as probably enough to get in the playoffs next year, but not strong enough to contend until a year or two after. You'd need the youngsters to mature into legit, solid NBA players quickly, similar to the way Rondo and Perk were able to contribute to the 2007-08 team.
That's actually not a bad team. Depending on the SG, it could be pretty well balanced on both ends of the court. If the SG is a good shooter, he, Love and Green would provide good spacing and weapons for Rondo to work with.
You would still have some future draft picks you could leverage to get additional help, of course. And if you get lucky, the Nets implode for that 2016 pick. I would try my best to NOT trade that particular pick.
So, I can see how it all could be made to work with (trading our #1 pick for) Love, but I'm waivering on my draft pick threshold for when I'd want to do it. Right now, I'm inclined to say, "No" if we have a top-3 pick and "Yes" if it's 6, 7 or 8. I think I'd want to wait to see who falls to #5, if that's our pick.
If we get a top-3 slot tonight, I'm leaning towards wanting to play it out more organically. Unlike some here, I really like all three of Wiggins/Embiid/Parker and can envision building with any one of them. But I'm not 100% opposed to trading for a star, either.