janhendrik,
I suggest that you study our example designs closely; usually in the top-level schematic in quartus we will explain the settings used in the PLLs. As far as phase delay two basic points apply:
1. Phase delay will be fixed for a given dev board. If you go off and make your own with different trace lengths to SDRAM, you'll probably have to get out a scope and measure the delay. We do this to determine phase delay in our example designs when we roll out a new dev board.
2. If you're just using our dev board, the same phase delay applies whether you're running at 40, 50, or 80Mhz. The trick: I say "phase delay" (expressed in nanoseconds) and not "phase shift" (expressed in degrees or radians). Our example designs' PLLs will have a phase delay in nanoseconds, like "-3.5" applied; if you keep this setting constant and bump the PLL output up to, say, 80Mhz, you'll be fine.