Need sine wave with most electric blankets and is better for motors in power tools. 2000 watts is plenty to power anything that plugs into a regular outlet. I would stick with 12 volts to allow the alternator to charge the batteries. Still need a good battery charger during moderate to heavy use to bring the batteries back to full charge.
GP inverter $8252 to 4 Lifeline batteries:
http://lifelinebatteries.com/products/marine-batteries/gpl-31xt/IOTA IQ DLS-30 charger $150 Custom 12v cables
http://www.genuinedealz.com/custom-cablesGood luck