I'm putting together a new system based on Intel Core I5-2500K and my plans have gone from using the integrated Sandy Bridge graphics with an H67 MB to a GTX 450 with P67 MB, to GTX-460. Now I'm thinking to be safe for a whileI better invest in a GTX-560. My present graphics needs are for CAD, photo and video editing, but maybe given the capability I'll find interest in games.
I presume anything more than a GTX 450 is strictly gaming territory (?). So what kind of games need this kind of graphics power? Are the higher end cards only needed for combat games, or would something like Myst benefit? What about simulation of cars, planes etc?
CAD can use the CUDA cores in Nvidia cards to accelerate rendering, but will never be as efficient at it as a workstation card like the QuadroFX. Those cards are very expensive. Any modern discrete graphics will offer benefit over forcing your CPU for the rendering.
Programs will always use as much power as you provide for them, there isn't such a thing as overpowered. It all gets used and will shorten the render time based on how much money you are willing to spend. Photo editing is more processor intensive and dependant on RAM and HDD read and writes. Video and 3D applications are demanding on all ends, using what you have with different parts of your computer taking over different aspects of the task, such as modeling, shading, Floating point calculations and texturing, but your CPU and GPU will also be limited by the amount of RAM you supply your composition with, because writing to the Hard Drive will have major lag-stutter problems, it all gets stored into your RAM which writes as fast as you create it. People will be quick to say anything over 6Gb is overkill, but a 30 second render @ 1080p 29.97hz will use all 6GB. Basically on the work end, the more RAM or a good solid-state, the better.
Game-wise, Myst can run on a phone. All of those older games (Journeyman Project) will run well on anything you buy. Racing sims are more demanding, it really depends on how old the game is that you want to play, because that will have to do with the amount of polygons they filled the world with and the texture detail. Anything less than 30 fps in racing will be noticeably stuttered. Flight simulators are a similar breed, when they were made will have dramatic quality and requirements variations.
The 560GTX is a more powerful card, but there are games today it will struggle with at highest graphical settings and high monitor resolutions. Strategy games typically use the most CPU power to track all the objects, anticipate moves and constantly adjust to your playing style, but that CPU you've chosen will be good for anything. There is a website that you can use to see how well your can run games, once it's built, know as (System Requirements Lab) Can You Run It?