That's just how RF names their amps, & you're thinking 600.2 0r 400.2, not x2 If the specs on an amp say 100x2 thats 100 times 2 (100 per channel) You are just totally wrong bro.
also with two svc 4ohm subs your options are 2ohms and 8ohms and two might not work with your amp as it would see 1ohm per channel bridged and a load of 8ohms would be about 100watts total or 50w per sub.
how the hell do you guys figure its going to be 100 per channel if it's 100x2 the x does not mean times that would mean my power series 600x2 and 400x2 are really 1200watts and 800watts if I run them bridged right?