Honestly, on that power, I'd see if you could score some shallow-mount IDQ. I assume they'll be closer to the SQ that you're after in your setup based on you currently running Kappa Perfects. And if I were to compare the IDQ to either the Sundown or the Skar, I'd still pick the Image Dynamics. You'll pay a bit more, but you should see some significant gains.
And, FWIW, I used to run a similar setup and have managed to make it look like a midbass driver in comparison to the single ICON 10 I'm using now. Even in a smaller, lower-tuned enclosure, it just performs and performs well. At this point, though, you've gone closer to double the cost of either driver you're considering. It's still worth the added cost. A pair of those on 1.5-2k ported would most likely make you VERY happy