2560x1600 First World Problems

OK, here is my issue.
I'm running my single 7970 in a mac pro. I've been wanting to get a 2560x1600 monitor for some time now, and I was at the micro center to get one last weekend, I ended up just getting some SATA cables. Will my 7970 overclocked to 1100 core and 2000 mem play metro 2033, and other intense games at 2560X1600 or possibly 2880x1800, at 120 FPS? I will definitely be using dual link DVI.
The mac pro uses EFI, so my current card's fans weren't controlled until I flashed the BIOS of the card. It almost caught on fire. To enable PCIe 2.0, I had to desolder a resistor, the resistor location is not known on the 290X. There is no EFI ROM for the 290X, so I will not see boot screen or be able to enter EFI on the mac pro, the fans will also not be controlled. Because the fans will not be controlled by EFI and the fact that drivers are not out yet for OS X, it will only work in windows with fan control software. If I get a 290X I'll need to watercool it. Crossfire doesn't work in OS X either. I've been wanting to watercool my 7970 for some time, but it's not reference card, and I have the memory running at 2000MHz. I need a full block, so I'd have to get a reference card somehow. In OS X, crossfire will not work, so for mac games, it would be useless. If it was a reference card, I'd just get another one and be done with this whole ordeal.
I am tied between trading my current 7970 for a reference 7970 and getting another 7970 to crossfire or just getting a 290X. If I got a 290X I could rig up an external GPU for my 15" macbook pro with the 7970, and not have to run the 6770M overclocked, about to catch on fire.

What do you think that I should do?

7970 will not play metro at 120 FPS at that resolution. getting another 7970 would destroy a 290x in gaming and cost way less. I think two 7970s will get above 100 frames(depending on your cpu) but don't expect it to be slammed at 120 all the time. In 99%  games both 7970s should get 120 FPS. when mantle comes out, for the games that support it, you will be getting 120 FPS on all the new games if its as good as they advertise it.

Yeah, you will struggle to get 120 FPS. Not that it matters. Those resolution panels are IPS, and they only display 60Hz, which is a 60FPS maximum. Dual 7970s will handle that really well.

I will overclock the panels.