A way to change NIC's MAC-address except with CLI ifconfig's "ether" option? Some ISPs do MAC-address port locking or/and use DHCP to assign IP-addresses to clients' network interfaces. Assuming you don't wanna bother calling them, what are your options then? If ifconfig's is the only one, where should it be called from so early during boot time that no Ethernet frame would ever went to wire with its original MAC-address?

P. S. Alas, there's no 'mac-address' tag yet and you need at least 300 reps to create one.Thanks to @gentmatt, now we have one. ;-)
You won't be able to permanently change the MAC address of the card, as it is hard coded on the card itself.  However, as you have guessed, you could create a script and run it at boot in order to change it every time the computer boots.    

This post details the steps it takes create the script and how to have it run when you want it to.  If you follow that, you should be good to go.