I would recommend the JL amp as well that way you can run the subwoofer at 4-ohms and the power will remain the same. Also 750watts of power on a type-r is fine. Now if your a little more budget conscious and would like to stick with Alpine I would recommend the MRX-M110. If you are running a ported box then the 600watts would be fine. You could also change the sub to a dual 4-ohm and run the amp at 2-ohms. That amp gives you roughly 1100 watts at 2-ohms.
On a side note if you are worried about your power supply in your car I would stick with the amp that you purchased because it is a very good amp. I would just change your subwoofer to a more efficient woofer. More power does not always mean louder. If you match the amp to a more efficient sub I think you'd be surprised. I would look into a JL audio w3 or even an Alpine type-S subwoofer. Good luck