So little update here, I tried the "video" preamp, AD828, it kinda sucks and does the oposite of what it should, it makes the signal less loud.
With the LMV358 sparkfun clone, I first couldn't get it to work with 3 different boards, untill the 4. did it, wich means the first 3 were propably broke. So if you order that one, get a bunch, test them and ask for a refund for all of them that are broke.
I also found this ready piezo preamp, again based on the video preamp chip and ordered one:
My experience with piezos is that you mainly need the high input impedance buffering. Unfortunately there is no info about input and ouput impedances with this little chip, but for 3bucks it's shurely worth trying.
I also got one of these lying around
Will let you know how it works/sounds.