Quad channel at different speeds?

[devilpup]

I've looked around and probably due to not wording my searches correctly I haven't found the solution.
I have the ability to run 4 sticks in quad channel. Right now I have 2x4gb Kingston Technology HyperX 12800 in parallel. I'm thinking of purchasing another 8gb kit.
Should I purchase the same speed or can I purchase faster sticks? Found a good price on the Kingston predators (19200) and if it'll benefit me they are the same price as the 12800's. I didn't know if the difference of speeds would hinder the setup in some way.

Someday down the road I might upgrade the current sticks for OCing.

Hardware:
I5-3570k OC'd to 4.4ghz
Asrock Extreme6
Kingston Hyperx 12800 2x4gb
Asus GTX 660ti turbo x2
Crucial M4 128gb SSD
WD Black 1TB HDD x2
Antec DF-85
CM 212 Evo

 

[Veziax]

You should purchase the same speed.So you'll be shure it'll work. You won't see the difference between 12800 and 19200.

 

[Tradesman1]

A few things here, you have an Ivy Bridge rig, so that eliminates running quad channel all together, IB is strictly dual channel...while you can go with 4 sticks and many do, 2 ea of the sticks will run in Channel A and the other 2 will run in channel B all four running effectively as a single 128 bit device. If you want faster or more DRAM best bet is a single set of 2x8GB in your preferred freq (some 3570Ks can run 2400, most all can run through 2133