Still, I don't think Zotac is the fastest. There are at least 2 other GTX670 cards that can go head-to-head against it, especially once overclocking is considered:
1) GTX670-DC2T-2GD5 (Asus Direct CUII) = GPU Boost 1137mhz
2) MSI GTX670 TwinFrozr IV Power Edition = GPU Boost 1079
Most importantly, please test the GTX670 Overclocked vs. GTX680 Overclocked vs. HD7970 Overclocked while using the fastest drivers from both camps (304.48 for NV and 12.7 Beta for AMD). 12.6 Drivers don't include the added performance boost that's included in 12.7 Betas:
The reference HD7970 Ghz Edition will be loud though since that XT2 Tahiti chip is really meant for after market cards and the reference HD7970 blower is lousy. Looking forward to your review. Maybe you should include Sapphire Dual-X HD7970 OC since those cards scale > 1200mhz at 1.25-1.3V, have cooling for the GDDR5 and are one of the quieter HD7970 offerings based on your testing.