What to look for in spec wise for graphics card upgrade?

When it comes to GPUs, most people don't actually look at specs in order to determine their purchase. Most of us look at benchmarks instead, but after benchmarks there are a few things you may want to look out for such as available VRAM (1 GB < 2 GB < 3 GB), the type of VRAM (DDR3 < GDDR5), the memory bus (128 bit < 256 bit), clock speed (900 MHz < 1.0 GHz) and attached heatsink.

Of course, this is only after you've looked at benchmarks and determined what model GPU you want. So let's say that you've looked at benchmarks and determined that the GTX 760 is within your budget and you like the performance seen in benchmarks. From there, you have a bevy of manufacturers to choose from with each manufacturer offering different versions of the GPU. You might like 1 model from ASUS because it has a good cooler, but you might like another model from Gigabyte because, although the cooler is slightly inferior, it has a higher base clock. Or you might see 2 GTX 760's from MSI which are the exact same, except one offers 2 GB of VRAM and the other offers 4 GB of VRAM, and from there it's a matter of what does your budget allow and what are your purposes? Is it worth the extra $30 or $50 or whatever it may be for that extra VRAM?

But again, benchmarks are really the most important factor. If you're looking at mid-range or better GPUs (which you probably are) and you've decided the base model you want and now you're looking at the manufacturer, then most of the time the only things you're going to be confronted with are:

VRAM Capacity - VRAM (Video Random-Access-Memory) is most important in displaying the number of pixels on screen (i.e. resolution). 2 GB of VRAM is more than sufficient for 1080p gaming. If you're going for 2560x1440 or greater, or you're looking at a multi-monitor setup, then it doesn't hurt to look at something 3 GB or more.

Clock Speed - The stock frequency of the GPU. You can overclock yourself, but sometimes it's just better to have a GPU which is clocked higher out the factory, because it offers better performance with no additional work.

Most other things like VRAM type or memory bus width or any of that other stuff are not choices you'll usually find at mid-range or higher GPUs. Usually GDDR5 vs DDR3 are only options given to lower or entry level GPUs, and most of the time mid-range or higher are only offered in GDDR5.

But yeah, benchmarks, as I've said multiple times now, are the most important. That and your budget.