I hear ya on not wanting to spend that much, but imagine if you add a UDP, Header, MP3 ECU and intake to the mix. The FSZE (owing mostly to those cams) has something like 170hp, almost as much as a MSP, and you'll be climbing the ladder fast with those cams. And, as is almost always the case on the FS, mods don't give linear increases in HP...it's the combination of different mods that really unlocks the power.
All that to say, I don't have $400 extra to spend on anything, and I don't think that I have enough experience or am adventurous enough to DIY, so cams are probably not in my future.