x58 boards are tri-channel so running pairs your going to be leaving a memory channel empty, will kind of take the advantage of x58 9xx series setup away.
edrik asked whether it'd be OK to buy 3 dual channel kits instead of 2 triple channel kits. That'd be 6 DIMMs either way. No empty DIMM slots.
I've read a lot of claims that there is no such thing as RAM that's optimized for dual, triple, or quad channels. As long as the DIMMs match, there's no problem.
I wish that I could recall the details of an excellent post I read a few years ago on the subject, but the gist of it may have been that manufacturers may use different timings on similar DIMMs in different kits. While the DIMMs are basically the same, the SPD (and XMP) settings would be different for dual or triple channel, as compared to single DIMMs.
That suggests that manually setting the appropriate timings would make the dual channel RAM work properly on a triple channel board. It might require some experimentation, though.
My only personal experience was going the other direction: I tried using 4 DIMMs from two triple channel kits on a dual channel (P67) motherboard. I never managed to get it to run reliably at its rated DDR3-1600 frequency. (The DDR3-1333 frequency was OK.)
I suggest getting the triple channel kits. The obvious choice would be RAM from the Asus QVL (qualified vendor's list) for your P6T Deluxe V2, but that list hasn't been updated since October of 2009. The RAM makers may offer compatibility information. If you're lucky, they'll even list RAM that works when all 6 slots are filled. You may have to back off the timings a little (manually, in the BIOS) to get reliable operation with all 6 slots filled, though.