If the Clips are stupid enough to offer Iguodala a deal starting at 12M with full raises then Ed is in a bind.
The financial issue is more the tax than the cap. With Brand's yearly raises, and the money we will pay Lou, the team won't have much over the MLE available next summer whether they sign Iguodala for 12M or Gordon for 8M. Even after renouncing Miller's 10M, they would only have between 2-6M left over, which is at or below the MLE anyway. The bigger issue is if they resign or trade Miller for a similar salary, then they might be getting close to the tax.
So basically the Sixers won't be using a large chunk of cap space to sign a FA anytime soon. The best they can do is swap Miller's 10M expiring for another player. Future acquisitions will have to be with trades or MLE type signings. Iguodala's contract effects his tradability and how close the team is to worrying about the tax- which could cloud the judgement about how to resign/replace/trade Miller and Sam over the coming years.
The Math:
With Brand + 10M cap hold of Lou and Iguodala the team is currently at the cap.
Lets say Lou signs for 4M and Brand's contract includes a 1M raise.
If the team pay Iguodala 12M (13M the next year) the team next summer would be 5M over the cap (or 5M under if the renounce Miller.)
If you sign or replace Miller's 10M and use the 6M MLE you are 11M over the cap. That puts you close to the tax. probably over the tax to fill out the roster.
Going with an 8M player like Gordon would leave you a few Mil more under the cap next year if you renounce Miller (but not the full 10M of Millers contract), and would give the team a bit of breathing room regarding the tax.
I can't say Comcast's feeling about going above the tax.