No, the SD12kD dont have a comp version, it is a VERY STRONG daily amplifier that we released because we needed to continue, considering we had the SD8000 for 2 years. We never stop creating amplifiers, for example, now that is released we are working on the next, a 24kW monster, maybe for 2010.
About the Joule effect (when the electrons chock themselves with the atoms of the conductor), the cable wont burn like a fuse, come on! I´ll explain:
The power dissipated on the cable will be I²R, so on a 1f 0AWG cable the resistance is 0.000096 ohm.
The power dissipated in a continuos 600A (remember, though, that by SD12kD playing music will flow 300 to 500A continuously) will be:
300². 0.000096 = 8.5W (300A each cable)
This certainly wont melt the cable!
resistance reference:
http://www.interfacebus.com/Copper_Wire_AWG_SIze.html