I have a Pair of the Kicker RS5C. I up them from some Rockford sh*t in my car. i would have to say it was a great up grade man. i just love them. they sound 200 times better then the old pair.
I'd go between the Diamond Audio M651 and the Kappa 50.5 CS, one you didn't mention that are worth looking at are Infinity Kappa Perfects, too. I've seen them online for about $250 in the right places, saw mine on www.ikesound.com.I haven't heard the Kickers or Orions, so I'm in no position to say anything about them. I do know Audiobahns are crap and won't last long at all.