mid-2011 27" iMac Nightmare

Ok here goes. Last year in October, about 2 weeks out of my extended warranty and immediately after installing Yosemite, my computer started making a buzzing noise. I had no idea what it was, so I contacted Apple and told them that this only started happening after installing Yosemite and I am right out of warranty and they were reasonable and said to bring it in to the store and they would check it out and fix whatever it was at no cost due to the circumstances. I dragged the computer into the mall and spent an hour at the store, and they did not find anything wrong with the computer. It didn't even make the buzzing noise that had been happening for the past few days. They wanted to keep it for a week, but I needed it for work so I said I would bring it back if it continued.

Throughout the next year, it happened intermittently, until this summer when the buzzing was persistent even with the display off. I thought it was a fan, but after researching on here and other sites, I determined it was the power supply. Foolishly, not wanting to spend 600-700 or however much they would charge me to install it at the apple store, I purchased an OEM power supply and put it in myself. I work in IT so I figured this would be no big deal. Doing so, I believe I accidentally bent the connector on the data display cable after putting the computer back together. I had no buzzing noise, but also no display. After looking into getting a replacement cable, I found that there was a recall on the Radeon graphics card for my exact model that could cause display loss, so I contacted apple about having them swap the card out. Went to the apple store again, they found out about the power supply and refused to even look at the computer, and also refused to replace the graphics card that was a company wide recall.

Now I am left with a $2000 computer that they refuse to fix or even honor the recall. This is awful. I understand their policy about fixing computers and I was willing to pay to get the cable fixed, so I am not that upset about that. That is my fault. But the real kick in the pants is that I should be entitled to a new graphics card, and they will not budge on that saying I voided everything by replacing the power supply.

Does anyone have any advice for what I could do? They never even mentioned the graphics card recall last year when I went into the store, or notified me in any way since it started in 2013. I feel super cheated here. I feel like if they really won't service the computer, the least they can do is just give me the graphics card and I will install it myself. Sorry if that was super long, I really don't want to have to shell out another 2k for a new iMac.