will wiring the sub to 2 ohm draw less amps per watt ratio that having it at 1/2 ohm if the are both pulling the same wattage. what would be a good choice of an amp too. i was leaning toward a soundstream pca 1000d which is rated at 800rms at 2ohm
also the sub is 900rms. would it be better to build a box for my hatch and if so is it better to face backwards/forwards, or upwards so it hits of the glass hatch. the box will be vented nontheless
from several tests I've seen an amp will generally be less efficient at ultra-low impedances. there are probably exceptions, but none come to mind.
As far as how to set up the sub. I used to have a Gen 2 RX7. I messed with several different box placements and found that placing it toward the rear of the car firing toward the rear gave me the best sound at the driver's seat.