A few quick newbie questions

Im kinda new at making gainclones, so far I have made 3 monoblocks. All three have used the LM1875, this is because it is all i can get my hands on. Ok so the quesion I have is: What will happen if I use a 12-0-12 supply for my GC? I have two 12V 4.5 AH SLA batteries, which I would like to use to power my 3rd GC. The datasheet for the LM1875 says the min Vin is 15 volts per rail, what happens if I go below this by 3 volts or so? Oh and one last question, has anyone had any experience paralelling LM1875's? Oh this is also my first post so please excuse my ignorance, im new at this;)