Most D-Blocks are designed to be 1ohm stable, as they're usually for competition purposes... If you're wondering about it, wire your subs up in series (1ohm) and see if they bump... the subs should be able to handle it, no problem, and if your amp ISN'T 1ohm stable, it'll more than likely go into protection mode (at least, mine always have). It's just a good idea to turn your gains and whatnot down before you rewire and test.... just to be safe