College Sr. Formal Dress--Want A Knockout One

I already have one in mind, at http://www.alfredangelo.com/default.htm, under Prom dresses and it is dress #3333. I`m about 5`6/5`7, 115-118 lbs. Long legs, so looking for one-shoulder pastel...possibly side slit for showing leg (and b/c sometimes it`s too hard to walk in straight, tight dresses!) I want something classy, but sexy at the same time... WOuld be sooo grateful for any suggestions, especially if anyone knows of online stores or dress sites!!!!!!!!!!!! --peace, seagreeneyes353@hotmail.com