[2 t2500.1s/ 2 RE mx 12s/ 2 Kinetik 2400s]

Ok i have all these things hooked up in my car... i dont have the big 3 done and i have a stock alt in my scion tc... should i do the big 3 even with stock alt? Also the real problem is i have this all hooked up right now and only one sub is working... the other sub moves but just barely and the amps are not slaved they are hooked up via rca splitters. This is not my first system by any means but its my first system over 2000rms. Any input on how to figure out if its the amp or sub thats bad? how to check phase, anything? Thanks

[amp efficiency]

ok so i have 2 t2500.1bds running off of 2 kinetik 2400's. thats powering 2 12'' re mx subs... now do you think those batteries are a good enough bank? and i havent doen the big 3 yet should i do that even with my stock alt? its all in a scion tc only has a 100amp alt....