Risers does open up possibilities, however, how much room do you currently have between cards and PSU?
If I needed to have multiple cards in close proximity in such a small case, they would be water cooled (or the core would with AIO).
I rather see the GFX being water cooled than the CPU as for most people in here (gaming) the GFX pulls considerable more power than the CPU.
In some instance it is reversed (extreme core count or OC).
If you want to give good airflow to the GFXs, you could consider moving the PSU to the back above the PCI-e ports, leave the top fans, yet only have support for a 120mm radiator. And then both GFX facing towards the side (though NVlink is a problem unless cables is made?).
This would also leave more room for a potential air CPU cooler. And if only one GFX is used the low GFX space could have mounting options for 240mm radiator (or even bigger air CPU cooler).
And then some mounting options for HDD/SSD behind the upper GFX in front of the PCH .
[MEDIA=imgur]0z99egu[/MEDIA]
