Performance (drop) can't really be predicted, as it is unknown how specific games use memory. I can't predict which games will show any obvious signs of performance decrease, as I haven't got the exact same system setup nor any of these games to test performance.
Remember that any memory rated higher than 1333 MHz will be downclocked automatically to 1333 MHz to match system. So the 1600 MHz memory will be run at 1333 MHz anyway. The only way to run this memory at 1600 MHz is to overclock it (and the CPU also if necessary).
Can't really recommend any specific Corsair DDR3 1333 MHz 4 GB memory as there are quite a few to choose from. Most of these modules should be compatible. If there is any doubt, let us know and we'll check compatibility.
If the 1600 MHz memory happens to be cheaper than the 1333 MHz memory, then get the 1600 MHz memory. Otherwise get a 1333 MHz module instead.