well, yeah you could technically run 3 pelts on the 12v line, You'd probably have to do the R82 mod to bump up the voltage.
seems like a waste of a power supply though, all those unused amps on the 5v and 3.3V lines.
You might want to get some 5V tecs to put on other stuff just for the hell of it.
Don't forget you need a load on the 5V line anyway for the PS to function.
This powersupply will power two, maybe three of those tecs and looks to be ATX.
also, at lower voltages, the tecs pull less amps, so @12V, those tecs would pull something like 6Amps each.