Olaf van der Spek wrote:
His third graphics card essentially sits on top of the PSU intake fan.
You'd put the PSU intake at the bottom, not at the top.
Then the PSU's thermal effect on the rest of the system is really no different from having the PSU on top with the intake at the top of the case. Then PSU placement really comes down to preference, as there's no objective advantage of either position over the other.
Right. Except, then there's a direct path for noise from the PSU to you. There's also the risk of something falling into the PSU. Ouch.