the sundown is underrated, the other two won't exactly be happy with much more than 1500 watts.
Ive owned and tested all 3 subs //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
the nightshade handed alot more power. the nightshade also costs quite a bit more doesnt it?
The RD alpha's are nice subs, I loved mine, but you will never be able to sell them for anything close to what you paid. I had a pair of the alpha v2 12s and they were sick subs, but when i went to resell them I lost my butt.
the level 4 is not a bad driver either, but the sundown sub is more of a spl sub made to be a daily driver. instead of a daily driver sub that can get decently loud.
hopefully this explains my point a little better if not let me know and i'll try and help you out more.
I'm by no means saying the sundown fits your needs better, but it is a class above both those two.