@danj I have a 2011 iMac with the i5 processor. My overall investment is really low in it thus far, and it's my current DD computer (I have other computers on hand just in case, however). I am going through with a processor upgrade, SSD addition, and GPU upgrade to put myself onto the newer Mojave OS (I want to keep 32 bit support for the time being). I understand that the i7 2600 TDP is greater and would put strain on the PSU, especially if I'm adding in an MXM-A card not designed for the system; I'm planning on using the Quadro K2100M. However, I'm having the same issue that the original user has. The 2600s is significantly more expensive than the 2600.
My question for you is this - could I get the 2600 and undervolt it to 2600s levels to keep the TDP down? What does your experience say would happen?