I have recently fitted 2 x Continental Grand Prix 4000S II (700 x 23c) and 500kms later this happens to the back tyre.

* If you can't see the image, its a tear on the tyre side wall with the new tube bulging through.
Now I need to get a replacement and I wonder if I should look elsewhere.
My riding is restricted to commuting to the city and club rides and that I'm not really a heavy person I'm considering these options in a similar price range:
Vittoria Corsa CX
Veloflex Master
GP 4000S II - yes, get the same and blame bad luck
Another thing to consider is if I should get a new set (and leave the other 500kms old Conti as spare) or get only one and run it with the GPS which also brings the question of where the new softer tyre should be fitted (front or back).
Your opinion is greatly appreciated.
Andre