Hi newcomer and welcome to the Tom's hardware forum.
If you want a 3-Way SLI or 4-Way SLI or Crossfire at x16, sorry but, none mobo support that.
Now for the option that Henry Chonski
says, sorry, but for your needs don't work too. That mobo is chipset AMD and you want a 3-Way or 4-Way SLI, for SLI you need a mobo with chipset nVidia that aren't good.
My advice? Today the best option for GPU is ATI, so, this
is a good mobo, that meets with your requirements.
Now, if you still want the SLI, you need a mobo with chipset nVidia or Intel, nVidia chipset aren't good with AMD processors, so, the way for SLI is Intel. Now the problem, Intel don't support AMD processors (don't ask why).