An equivalent of the a fully cambered, stiff carver like the 4x4? You'd have to go with a race-oriented ski from Atomic, Head, Blizzard. I have the 4x4 and it's a speed demon, holy crap it loves to go FAST. But it's a great deal of work too. Also not terribly versatile either; forget soft snow and mogul runs unless you're an expert and top notch physical shape (which I'm not in either category).
However, if you're concerned about your skill level, look at some of the more intermediate-advanced frontside carver skis. There are plenty out there that could work very well for you, but nearly ALL of them will not be like the 4x4. The new ones will feature some rocker and other features to make the ski more "friendly and accessible" than the traditional cambered carvers like the 4x4.
The new ones should be less demanding but still provide you with what you're seeking, and allow you to grow into them as your skill level increases.