I dunno, locked voltages on a non reference card that's touted as having an awesome cooler doesn't sound like a smart move from ASUS to me. My lifetime GFX OC experience is limited to a slight MHZ boost here and there (mostly due to wanting a reasonably quiet rig when gaming), but I wouldn't shell out the $20-30 (last i checked) more for a DC2 for no reason.
I'm not sure that the voltages are actually locked. It appears some people in the reviews say the people who are complaining about locked voltages just don't know how to overclock. It's completely possible. Say someone downloads MSI afterburner and doesn't know about enabling the unofficial overclocking option, they may think it is locked. Honestly it doesn't matter to me, if I'm going to be overclocking it will be in the BIOS, and thankfully it comes with a BIOS switch.
I got a sapphire 7970 refrence design from day 1 that it was released, and i recently bought a XFX double dissipation.
Since the cooling of the XFX does NOT exhaust the hot air but simply dissipates it, it heats up everything around it. But at least its quiet... i can maintain a 1100mhz GPU clock speed without crossing 80°. Good or bad, that's up to you. I kinda think its ample.
Same cannot be said of my sapphire refrence card. Its loud as hell, but at least he exhausts the hot air. but you shouldnt care about that card. Because it doest exists anymore. But at least it had a BIOS switch. One i have never needed though.
Anyho. the performance of the 7970 is Good. I don't know what the reviews tell you, but you defenitly get your bang for a buck. There really is a bang present. Only downside is that its more power hungry.
But yes. It really is kind of sad that my refrence card has (apperantly) more features than a modified one.... My Saphire even has unlocked voltages.... Oo ... I have to recheck that my xFx has locked v's or not. I thought it was locked because it was greyed out, But i havent really looked for it. If you want me to, I could really search it out for you.
Naw mate it's ok. I've pretty much put my heart to getting the ASUS card anyways. It's a shame a company that can make such sleek cards like XFX might lock voltages or leave out things like BIOS switches. Thanks for all the info though.