I'd suggest starting with the reviews at photozone.de. He has covered most of the Nikon primes (except for some of the latest) plus a number of third parties.
Be careful. It is a matter of taste/preference with regards to primes. To me, if you can't shoot a prime wide open / widest and need to stop down much further to a smaller aperture to get a sharper image, then I'd less likely consider that prime. Then again, people's acceptance to sharpness varies. For some, center sharpness is enough - no need for extreme border/edge sharpness. Whereas, some would go for all. It depends on what you need the prime for. Portrait or landscape, etc? For the latter, many would prefer edge to edge sharpness - whereas Portraiture may not require such sharpness (as long as center is sharp, that would do). Some primes are not sharp at all, wide open, largest aperture... That doesn't mean you can't use it - it probably depends on how you use it as well.