I don't think it will be much of a challenge to find something more demanding than that S3. Volkl is claiming this year's Mantra to be "The Best Mantra Ever", and you know, I'm not inclined to disagree. The thing still hold a bad ass edge on the groom, but is much more pliable off in the fresh and chunder. I've always been a fan of Salomon's "Lab" skis. I'm putting my money on the Q-Lab this year……I suspect you'll find this Salomon plank to me "way more demanding" than your S3s.
I am not sure it is the "best Mantra evah.." but I do think it is the a better Mantra for more people than the past few generations. I do agree that the Q-Lab is a ripping 104mm ski and at the top of it's class.