Will this be loud enough?

hey guys i have 3 questions...
#1 which is better to power 2 subwoofers, a class D amp with 600rms x 1, or a 2 channel amp with 300 rms x 2?

#2 do you guys think two alpine type R swr 1221D in a custom ported box, will be louder than my current setup, two sony p5 12's with 350rms each actually getting 350rms from a 4 channel amp?

#3 right now, like when i turn my system up, like my hair starts shaking n other stuff like that, you think two type Rs with 300rms each or 600rms into two type R's will hit harder? or what im trying to say do u guys think this is loud enough? (im saying this mostly because i want a custom ported box and no dual 15 boxes fit in my car, and everything else just cost way too much, like a 800rms+ amp)

1 - Doesn't matter, it's the same either way
2 - Yes, and they'll sound better too
3 - Only you can say if it's loud enough. For some people 150dB isn't loud enough, for some people 110dB is too loud.

The advantage of the class D amplifier is efficiency. The class D will draw less current than a class AB amplifier. A class D mono block amplifier however, is typically limited in its bandwidth and therefore cannot drive full range speaker or really anything other than a subwoofer. If you are at all worried about your lights dimming or otherwise the electrical impact, the class D will be a little easier on the car's electrical system. It doesn't break the laws of physics though so it is still going to draw a considerable amount of power.