for the most part rl programs go heavy on the video card than older generations, the 30 series gpu isn't very strong, you can't go by the first number with the nvidia gpu, you go by the 2nd number - the first number is the generation, the 2nd number is the architecture - so the 830 is the 8th generation from the 30's series architecture. The higher the architecture, the better cooling and the more resilient it is to heat, which is ultimately the limiting factor on your video card speed. How fast your gpu can process depends on being able to do x amount of calculations within a level of heat that won't cause your video card to melt. Basically the 80 series architecture is capable of doing more calculations at lower heat levels, than the 30.
That said, the 30 series would have to disable a few advanced features to keep the gpu from running hot. Once a gpu starts running too hot, you will experience software instability and artifacts.
bottom line for cg programs in general, you want a computer that can stay cool while doing lots of processing.
Incidentally this is why overclocking is considered dangerous, basically you are making a processor run hotter than it was normally designed to withstand, this is why the big deal with overclockers is advanced cooling systems. ie - water, nitrous oxide. - in extreme modes it becomes a game of not freezing your cpu into a lock from a nitrous oxide blast, while pushing the heat of your processor to a level that rivals molten lava lol.
edit - another thing to consider with "real time" renders, real time means massive bursts of data to give you quality graphics, massive bursts of data means heavy calculating to keep up with the bursts of data coming from the software. by it's very nature, anything "Real time" is taxing on a cpu / gpu - especially when calculating 30 hiqh quality frames / images per second.
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"To define Tao is to defile it" - Lao Tzu