mmcguire,
IMO, with a pool/spa you'd be best served with a gas fired 400K heater if you want a quick heating spa. If you feel that the luxury of waiting time is on your side go for the defrosting heat pump.
Solar heating and blankets do wonders on keeping and slightly escalating pool temps, but don't help on your spa.
If you feel it's in your budget step up to a combo set up with both a gas fired heater and a heat pump. it allows you the best of both.
I have a rather large pool and use the combo setup. I can begin my season earlier and extend it later with my heat pumps and heat my spa rapidly with the propane fired heaters.

Thanks for supporting the industry with your new pool purchase, you'll soon find out what all the hoopla of pool ownership is all about. I promise you, having a pool at home is the best thing since sliced bread!!!

See Ya,
Kelly