If you want water cooling, you need to do a custom loop that goes to your first GPU's water block, into your second, and back into your radiator. This requires more than your run of the mill H100.
1. Awesome name, I totally dig it. 2. The corsair H100 is just a CPU cooler, it's not a complete system liquid cooling kit. 3. Your videocards if running at factory speeds will be completely fine with the built-in vaporchill cooling that's on the 5xx-series cards. there's no need to cool your videocards with any aftermarket cooling unless your case does not dissipate heat well, or if you plan to OC the heck out of the videocards.
You would have to mod it, but it can be done and easily too? I think. I remember stumbling upon this, didn't read too much into it, so I don't know how easy/ hard it is...