It's oft stated that the factory overclock cards are the same thing as the reference models and that you can do the same OC yourself. This couldn't be further from the truth.
For example:
The EVGA reference card has 4 phase VRM and stock cooler
The EVGA SC has a 6 phase VRM and improved cooler.
The EVGA FTW has an 8 phase VRM and improved cooler
The better the cooler, the better the voltage control stability wise and the more voltage ya VRM can handle w/o going up in smoke, the faster the OC you can obtain.
Based upon my experience with the 560 TI's.....
820 - 900 MHz was doable with just about all of the reference cards
900- 980 was doable with the improved coolers and 6 phase VRM's
980 - 1070 was doable with improved coolers the 7 phase VRM's
Personally, I have had much better luck w/ the Asus DCII TOP than any other card lines I have tried.
As to whethrr it's worth the price.....Id say no as long as the Asus TOP model is around