The "white cast" is most likely due to physical sunscreen ingredients like zinc oxide and titanium dioxide... they provide a physical barrier between the skin and the sun (so the white cast makes sense). So I suggest avoiding these ingredients if you want something that doesn't cause a white cast.
I've personally used Neutrogena Ultra Sheer Dry-Touch with Helioplex sunblock under my foundation. I like it cause it's not greasy. In order to get good sun screen benefit, you need a product that says "broadspectrum coverage" with at least SPF 35 (that is the minimum for manufacturers to claim "protects against skin cancer"). I don't know for certain if cosmetics with SPF are broad spectrum. There hasn't been much proven benefit going over SPF 50, but it's probably not harmful.
It is recommended to reapply sunscreen at least every 2 hours... (no matter how high your SPF is) which isn't really practical when you're wearing makeup. I try to wear a wide brimmed hat instead of relying solely on the sunscreen.
Hope the information helps. Whoo pharmacy school.