I think you'll find a lot of pilots have been through the Rayban/Oakley/Randolph/Bolle/Blah products and many have ended up with Serengetti - where they stay.
Look for the Drivers gradient lens which works well with EFIS. Personally I like the Lassen frame but whatever suits you. I think they are about £170 but the titanium frame and the engineering on the hinge means they will last a mighty long time.
Cheers
WWW