wiring 1 amp to1 sub but what ohm rating

I have just bought an alpine type r 12inch 2+2ohm DVC subwoofer, then i bought an alpine mono amp which is rated at 4ohm@200w RMS and 2ohm@350rms, i can wire up the sub at 4ohm with 200w rms 1amp-1sub setup or i can wire it up at 1ohm 1amp-1sub setup, but i know how to wire up the sub at 2ohm so i get 350w RMS but it doesnt show it in the instructions how to do it at 2ohm as possibly the subwoofer is not supposed to be run at 2ohm, so basically is it safe to run it at 2ohm(single amp single sub setup)? whats the difference between 4 and 2 ohm? is it not worth the extra 150w RMS what would i gain from the extra power?

Thanks for any help!