As SC suggested there are a lot of really good skis to choose from and the East vs. West question is key. Judging from your self described terrain preferences I'll peg you as a Level 6 ish? skier.
So.....what do you need to get better? Well #1 is training. After that, equipment can help but the wrong equipment won't help. A particularly stiff ski is not the correct call. You need something stout enough for your weight, aggressiveness level, and the speeds and terrain you will encounter both in the near term and also in the longer view. So far you have been suggested the Volkl AC30 and the K2 Sidewinder/Crossfire. Those skis are about as similar as eggs and apples.
AC30: Pretty good shape and waist width but too stiff and agressive.
Crossfire: This ski is on the stiff side too but not as bad as the above and more manageble. This is a fairly narrow ski, would challenge you a bit and could be a doable choice if your main goal is groomer skiing
Sidewinder: Very nice shape with a soft flex, Pretty good for where you are right now, but may not be great if you improve much.
A ski that is comparable to the aggressiveness of the Crossfire but with a more versatile shape is the Nordica Nitrous CA. It is also about $200 less than the Crossfire and is one of the classic skis on today's market.