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You'll get a range of answers but what I seem to see the most is that "best" depends how you use the car. It usually comes down to 3 options if you are looking aftermarket shocks.
Daily driver and road trips? Bilstein B6
Lowered and/or aggressive driving, want more performance, and are ok with a firmer ride on the street? Bilstein B8?
Want the best performance with a stiff ride? DRM Bilsteins
I just recently upgraded my 07 coupe to a Z51 suspension package. So, stock Z51 shocks, sway bars/bushings/links and front spring. I left the rear spring alone as the base one is very close to the Z51 spec. All together it was about $800 (bars and spring were from Ebay). I did the work myself in an afternoon and am very happy with the firmer (but not too firm...) ride.
I replaced my OEM shocks with Bilsteins several years ago and many miles ago and they are still doing OK. They have three different levels. I have the base suspension, I believe there is a shock for the Z51 option. Best price seems to be with Tire Rack.