The 970 Extreme3 has a cooled and good quality 4+1 phase VRM system (akin to the one on the 970 Extreme4). Where 4+1 phase VRM systems are a problem with 125W TDP processors is when there is no cooling (i.e. M3A770DE mentioned above) or when (on top of that?) the design is mediocre and failure prone (i.e MSI board above).
By the way, the lower overclock result may be a result of differences in motherboard. If the sound chip on your Extreme3 is different from your other board and might be more strenuous on the CPU it may be holding back your overclock (yes, integrated sound cards can hold back overclocking potential because sound processing is done on CPU). A sound card will help here. Given that your board is probably of a newer chipset than the old one (970 vs whatever?) it should overclock better when misc issues like sound are aside.