"Future proofing" (but only to a certain extent.)

[Wyatt]

Been a long time since I've made a thread like this.


I'm trying to "future-proof" my PC, but only to a certain extent. I don't expect to play games perfectly that come out ~4 years from now. However I don't want to be buying another card by the end of next Summer.
The three things in need of an upgrade right now are my motherboard, my CPU, and my GPU.
Currently I've got running:

Kingston HyperX 8gb DDR3 1600mhz ram.
Western Digital 7200 RPM 750gb HDD. (Dedicated to music, games, and shows / movies.)
Seagate 7200 RPM 500gb HDD. (Dedicated solely to the OS, and small programs.)
ASUS M4A87TD USB3 Motherboard. This board does not support newer chips, but the board itself has surprised me greatly all around.
Sapphire Radeon 6870 1gb. This card has chugged along, but I can definitely see how it's aging..
Phenom II x4 975 BE. This chip was great, and it has done everything I've been asking it to. However I'm moving into 3D Modeling and a lot more "strenuous" video editing. I can definitely feel the age of this chip when I'm doing anything that would even attempt to push it to its limits, so to speak. (Rendering, 3D modeling, etc.)
CoolerMaster Hyper 212 PLUS Cooler. I mention this because I hope that this cooler will support the chip that I decide to upgrade to. If it doesn't, it isn't the end of the world, but I still hope.

I'm not sure what I want to buy and so that's why I made this thread. For months I've had my eyes set on the Sapphire 7950 card, but recently the 760 cards have caught my eye. PC Gaming seems to be leaning more toward nVidia nowadays, and so I thought perhaps an nVidia card would be a better choice.. Of course i haven't settled on anything.

Between the three parts I need to upgrade, I'm looking to spend no more than $600. What are my three best options based in this price range? I'll be posting a few items here as I find them on Newegg so I may ask you guys for opinions.

Thanks!