The 2600 routinely beats a 8400 with 50% more cores and a higher turbo boost (the 8400 does do better in some titles) which means it's definitely an upgrade from a 7400 not saying I'd necessarily make it but I doubt there's any game the 7400 would win by more than 5% and something like bf5 the 2600 is solid and in places a 7400 would be a stuttering mess