Using an RCA cable splitter into subwoofer

Now that I just set up a new subwoofer, I got to wondering if it would be best to plug into both RCA inputs on the back of the sub or just one of the two.  My processor has two subwoofer outputs and I'm using two identical subs.  So I use two AQ subwoofer cables out.  Does it matter just plugging into one of the two inputs or should I get a hold of two AQ splitters?