Re: This G.Skill DDR3 1333 7-7-7-21-2t at 1.5v is crazy good.
The reason they recommend not to use it with your socket 1366 is that you have a tri-channel design, while this kit comes with 4 DIMM, for dual-channel.
Not sure which configuration you are currently running (dual? Tri?).
And yes, memory has improved quite a lot in the past few years Most kits sold today are actually 1600+, although they may not be marked as such. Quality is just that good...
As the universe is curved, there cannot be a straight answer...