Ninjalane has compiled a list of the best Intel X79-based motherboards you will never see, due to high pricing, (extremely) limited availability, or a combination of both. You can view the boards in all their glory over here.
It includes the Foxconn Quantum Force Quantumian-1, which was available only in Asia-Pacific and in limited numbers, the MSI Big Bang XPower II with spotty availability, the Gigabyte X79-UD7 OC, which is no longer in production or being sold,
and the Asus Rampage IV Extreme, which is available but with a high pricetag.
All of these motherboards have been used in the Ninjalane Labs as either review samples or as part of an online overclocking competition. In terms of overclocking performance X79 was quickly eclipsed by the LGA 1155 Sandy and Ivy Bridge processors due to better overclocking performance and lower overall cost. LGA 2011 might have 6-cores and hyperthreading but the same BCLK limitations existed giving you a maximum BCLK of 105-107MHz (not including the BCLK mulitpliers). K and X Sku processors offered multiplier adjustments but even with that the average overclock was limited to 5.3GHz. .