Crosshair iv formula memory

Hello all,

I'm upgrading my system i.e. mobo memory and CPU and i have chosen the X6 black edition and a crosshair IV Asus mainboard. I'm not so sure about the memory modules that i should purchase. I have the following restrictions for the memory based on a few consideartions. The Asus recommended memory list doesnt contain my desired configuration and i understand that there are a few configurations that work only on X6 CPU's (if anyone can expand o that i would be gratefull)

-lifetime warranty
-greater or equal with PC1333 standard
-need 2x4gb or 4x4gb for a initial 8gb or 16gb configuration(depending on price)
-fully compatible with the mainboard / CPU
- timing - please advise options as needs to be a good balance in between price and speed
-any other options for ECC based memory modules(kind of expensive)

Thank You in advance