I thought Rs could handle much more than ratedif you wire one type r at 1ohm on an aq1200d you'll fry that thing, you're more than doubling the power. get dual 4 ohm wire it to 2 ohms(still over powering this by more than 300rms) but if you get two dual4ohm type rs you can wire them to 1 ohm and run 600rms to them which would be fine.
this sounds like the best thing, if you plan on buyin another sub down the line, just save up another $140 or so and get two, you'll be a lot safer, and end up being cheaper and less of a hassle.y not just get both subs at once? then u wont need to get another box or anything. how much u payin for them techronics has em for 130$ shipped.