Well, if you look at the specs of a video card, you will see things such as shader clock, core clock, and stream processors and CUDA cores. (CUDA is strictly Nvidia) If you compare a Phenom II X4 945 (3.0Ghz) vs. a Phenom II X4 955 (3.2Ghz) which will win? The 955 of course, but if compare a 2.93Ghz core i7 to a Phenom II X4 955, (3.2Ghz) which will win? The 955, right? Wrong, the i7 2.93Ghz runs on a better architecture. The same rule applies to GPUs. (Graphics Processing Unit) So, if you took a hd5850 with the standard base clock of 725Mhz and standard memory clock of 1000Mhz vs. a hd5850 with 765Mhz base clock and a memory clock of 1100Mhz, the one with the 765Mhz and 11000Mhz will win because of the higher clocks. There are also stream processors and CUDA cores to take into consideration. So a hd5850 has 1440 stream processors where a hd5830 has 1120. So if you had a hd5850 standard clocks, (625Mhz core, 1000Mhz memory, and 1440 stream processors) vs. a hd5830 standard hd5830, (800Mhz core, 1000Mhz memory, and 1120 stream processors) the hd5850 will beat the hd5830 down. So, when you look at GPUs, you will want new architectures. The 440 and the hd 5770 are both from the same release times, but the hd 5770 is stronger. So, a GTX 560 (820Mhz core, 1640 shaders, and 384 stream processors) vs. a hd4870 (750Mhz core, 900Mhz memory, and 800 stream processors), which will win? The GTX 560 will win due to new architectures. Nvidia cards will basically always have lower stream processors, but that is because they use what is called CUDA. CUDA is twice as strong as a ATi/AMD stream processor. Those are the basics to GPUs. If you have more questions, just ask 'em! Hope that helped!