Which Vengeance? Newegg has 18 entries for Vengeance 2X4 DDR3 1600. (Some of them are just different colors.)
Newegg.com - Computer Hardware, Memory, Desktop Memory, Corsair, 8GB (2 x 4GB), DDR3 1600 (PC3 12800)
The version with the quickest timings costs about double the cheapest.
Newegg...