Nemozzz :
So which one should i get? 770 or 760? Also does bottlenecking mean it will also have a shorter lifetime? Does it cause any damage?
Bottlenecking means that due some part that cannot keep up with the rest of the system performance, it won't reach it's full potential.
For example, imagine that your GTX 770 can give you 100 FPS in a given game. If your CPU isn't able to keep up with this game cpu orientated tasks, the effective frames per second may drop under 100, thus meaning that you aren't using "100%" of your GPU.
Even if your CPU do bottlenecks the system in some games, it can drive the GTX 770 in most cases and hence if you want one GTX 770 and have the cash for it, I think you should buy it.
It's absolutely safe and does no harm to the hardware to have a bottleneck.
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But beware: You must be sure that your PSU can handle the GTX 770.