i would get the regular evga 580 for three reasons. Temps, noise and power. I was going to buy one originally but after reading alot of reviews i stayed away from them. The 580 is a great card either way you go. The vram is nice but only needed if your running higher resolutions or multiple monitors. The 580 isnt the quietest card to begin with, not bad by any means but once it hits 70% fan speed you start to hear it. Ive read multiple reviews about how the classifieds are loud because the fan is cranking to keep the higher temps down from the cards clock. Which leads to my other reason, they run alot hotter. Sometimes 5-10c more than a stock gtx 580 from some of the reviews i read. Which can also cause more of an issue later down the line with SLI when you got two of them closer together causeing the temps to rise even more. The other reason i stayed away is the power. They use more power to run and instead of 2 6pin connectors they use 3. Which depending on your PSU can be a problem if you plan on doing SLI. Just to use 2 cards you have use the connections you would to power 3.
Over all in my opinion the gtx 580 stock is a beast. Id rather lose the little frames per second to save my ear drums, and not have to worry about temps as much especially if your planning to ever SLI someday. If your running water cooling and all that it would be a different story. But im all set with that theres just to much that can go wrong. Better to stick with air. But the stock 580 can max out any game you throw at it. I got the SC version and maintain 60fps, in bf3 with everything maxed. Same with cysis and i get about 45-50fps in metro 2033 (should be better, but that game is poorly optimized. Any other game ive played it cranks out 60fps without breaking a sweat. If anything pay extra for a SC version or just clock you a stock gtx 580 to the SC speeds. The cons out weight the benefits unfortunately. Not to mention the price (which is always going to be higher than a stock card) no matter how much of a price drop they do. Classifieds are great for enthustiants who got the money to blow to throw at benchmarks and all that. But its not needed for a normal person who just trying to every day game. Hope i helped your decision a little cause i was in the same boat as you and after doing a crazy amount of research like i always do this is the conclusion i came too.