i ran my kx 2500 @ 1 ohm daily off 13v and it was fine even with a daily beating durring the winter. now during the FL summer with the amp already hot as balls when i come out to the car i would be hesitant to run it at 1 ohm. however even with the blazing hot sun and an already HOT amp the kicker does great at 2 ohms even with these horribly conditions. the kickers are built like tanks, you can put through hell and back before they blow. i've heard time and time again the p3000.1's arent as solidly built and below 2 ohms they fry.
this is the 2nd kx2500 i've owned and i'm more than content with it. it's efficient as all hell, looks sexy, and performs even with tons of abuse time and time again. either kx or zx you can go wrong. thats my vote....