I love my SKX, but I don't think I'd recommend someone try to buy one now unless they got a massive deal on it. The prices have skyrocketed, and it's no longer worth it. The 7s26 movement isn't really all the great, although it will certainly take a beating and keep running for many years. For the money that SKX's are going for now, I'd just suggest someone get a tuna, turtle, or a monster instead.
You're spot on about the 5KX crap though. I don't understand why Seiko did that. All they had to do was put the 4r36 movement inside the SKX case (which I think are the same as the 5KX ones) and drill out the lug holes. Presto - new, updated SKX. Instead they give us a diver-looking watch with less water resistance and a higher price.
In my opinion, one of the best bang-for-the-buck values in dive watches come from Mido. Yeah, they cost about twice what an entry-level Seiko costs, but you get Swiss made watch with a fantastic Powermatic 80 movement. I have the Mido Ocean Star Tribute and the thing consistently runs +1-2spd. And it has the most comfortable bracelet I've ever worn, with a ratcheting extension that is perfect for the warmer months when my wrist swells during the day.