Yup, you'll need a nice, big starter. The rule for yeast starters for ales is
Code:
Target yeast count = (4 billion) * (point of O.G.) * (# of 5 gallon batches)
Double that for lagers. So if you're making a 5 gallon batch of lager with an O.G. of 1.055, your target cell count would be:
Code:
4 billion * 55 * 1 * 2 = 440 billion
A single Wyeast smack pack yields 100 billion cells, so you'd either need 4 (and a half, technically) smack packs, or you'd need to step a starter up to 4 and a half liters (do a 2 liter first, then cold-crash, decant, and step up to 4 and a half liters).