Pentax K-X - Which SDHC Card

I cant seem to get a decent answer about which SDHC card would be the best for this camera, Class,2,4,6 etc.

I don't want to spend a bucket load of money on something that I cant tell will make a difference, any suggestions will be appreciated.

What about a Toshiba 16gb SDHC Class 4 Card, on special at the moment or will I be wasting my money ?