I rarely disagree with my fellow Pink Team brother, and this is no exception. If you want the best bang for your buck, then follow his advice. Otherwise...
500W is ok for any single GPU. It is possible to SLI with another 760 later on but you will need a higher wattage PSU for this. Why did I choose Zotac? It was the cheapest one. That's pretty much it. You can get any card you want. Gigabyte, Asus, MSi, Zotac, Galax, PNY, doesn't make much difference in terms of stock operation. When you go to overclock the various aftermarket cooling solutions will make a difference. The better the power delivery section and the better the cooler the better the overclocking potential. But GPUs are just like CPUs. Sometimes you lose the silicon lottery and even the great aftermarket card you get won't overclock very well. I'm not familiar with any 760 where the GPU is "binned" or "cherry picked" for optimum overclocking performance. Basiclally, grab a cheap one. It's all you need.
Having said that, Manu 2b's suggestion is a good suggestion. Getting the CPU and board used will really save you a ton of money, and an R9 280X (better yet an R9 290 if you can get it cheap) is much better than a GTX 760, and those cards have 1 and 2GB more VRAM than the 760, respectively.
Previously enjoyed hardware=cheaper=higher performance for less money. I agree with Manu2b about getting certain parts new like the power supply.
It's your choice, either way you will have a half decent gaming experience.