Yes, Giga board p67 or z68 have a bug in the usb 3.0 turbo mode where usb 3.0 gain a bit of performance by accessing directly to the pcie. I think disabling the turbo mode can fix it without much performance hit on usb 3.0. But since it has know problem, IMO, I will try to avoid it.
If you are going for a 2600k sli build, then you are building a performer and you are going to get ssd sometimes, correct? I am not a big fan of SRT. My reason for that is because I have a large enough ssd for all program and os and for storage, the files are sequential and a normal HDD on usb 3.0 or esata is fast enough for that. Also I am not sure how SRT affects the wear level on ssd since I don't know how often it will refresh and rewrite my cached content. So I will go for P67 to save some money and invest on better ssd.
People are saying Asus Sabertooth is a poor board because of the thermal guard right? Its purpose is to help cooling, so I doubt a reputable company like Asus will release the product if the guard makes the cooling worse. Even if it does overheat, they are removable, just remove it. So if Asus Sabertooth worked with you before, get it. Nothing beats personal experience.