I agree, a fast prime is much more valuable to me than a slow zoom. However, I would prefer a longer prime... the m.Zuiko 45mm f/1.8 would be my ideal choice.
The 25mm range is also nice though... such as the Leica 25mm f/1.4, Voigtlander 25mm f/0.95, or Lumix 25mm f/1.7.
I guess since you're bundling it with the GF-2 though, that you don't have much choice except the 14mm f/2.5. Not unless you get the GF-1 instead for the 20mm f/1.7.