Welcome to epic -
Have you got properly fitted boots? (Properly fitted = fitted by a professional...) If not then there'd be no point in buying skis, boots first (and everyone here will say that...).
It's gonna be pretty hard to find something that performs well in the 50/25/25 ratio you want.
The Theory, as far as I know, could work, but you'd need to decide whether you'd want them more for park (in which case I'd say go 177) or powder (186).
Whilst I don't know much about the Panic, it looks like it'd be better for you than the Theory simply because you can get it in 181cm, eliminating the length problem whilst still not being too thin. Good thing is as you only weigh 150lb you're not going to need anything properly fat to get float in powder.
K2 Iron maiden is another one I'd throw into the mix, 179cm, 90cm waist, twin tip - Powder mag described it as a park ski but I'd say its pretty capable in Powder and very much so on piste. Also, Iron Maiden.
However, depending if you want to do more park in the future (which is what it sounds like to me), it might make more sense to get a decent mid-fat for piste and powder skiing, and then find a cheap park ski to set out with, as you'll probably tear the park ski to pieces quite quickly.
Hope that helps...