Hooking up two subwoofers

 Hi all.  Currently I have two Martin Logan Dynamo subwoofers hooked up to the pre-amp outputs.  The left and right output wires go to one subwoofer, and then there is a wire linking the second subwoofer to the first.  I am wondering if this is the best (or, full range?) choice?   Could I, for instance, use the Krell amp's single ended inputs instead?  Now, the Krell amps speaker inputs from the pre-amp are balanced, leaving the single ended inputs available.  Or, will this not work or harm the amp?  Thanks. -Bob.