Gtx 650 will bottleneck?

Your GPU won't be massively overpowered for it if that's what you're asking. Since you game at low res, more will be on the CPU than at higher resolutions. It's absolutely fine though. GTX650 is comparable to a Radeon 4870, which was around in that same era.



No one knows what kind of specs GTA 5 will require at this time, but I can say you should at least be able to run the game with a GPU like the 660.

As far as the CPU, like I said, no one knows what the minimum system requirements are, but I would recommend trying to get an upgrade for it though.
Bottlenecking is term thrown around far too much, and often by people who don't really understand what it means. A bottleneck is basically the point in the system that constrains performance. Like how the neck of a bottle, being the thinnest point, is the part that constraints the flow out liquid out of the bottle. If your CPU is underpowered relative to your graphics, it won't be providing data fast enough, meaning your system is CPU bottlenecked (since the GPU could run faster if data was being provided more rapidly by the CPU). A system will always have a bottleneck - some component must constrain framerates. The goal is to make the GPU that bottleneck, so it's performing at its full potential.
All games are different. So while one game may hit the cpu so hard to can not feed the video card data fast enough, another game may hit the video card so hard the cpu would be waiting.

I do not think it will be too bad with a 650 as it is a mid end card.

An image of the power supply sticker can go a long way.

The important part is in red. If you have one rail, we need its rating, with 2+, you need the combined(not a simple add operation). Why a 300 watt power supply? because I had one handy to take an image of :) This little thing even has the 6 pin PCI-E plug.