I'd just like to thank Stereodude for being thoughtful enough to create my very own thread for me.
Unfortunately, I currently work 7 days a week while struggling health-wise, so I haven't been able to give this thread the attention it truly deserves.
The obvious way to improve cooling on the Corsair 600Q is to flick the premium Gold PSU and use something cruddy - the SPCR review used an old 80 PLUS
Bronze PSU, which all else being equal, ought to suck more air out of the top of the case.
But you may not be keen on that solution.
A handy explanation from SilverStone
A graphics card with a blower fan that exhausted out the back would also have helped.
But I guess a third GTX 1080 would be a big ask.
The GPU problems are similar to those faced by the much smaller Silverstone TJ08E, which also has an inverted motherboard with the PSU at the top. That case doesn't leak as much, but as CougTek found, the large fan at the front that is meant to cool the entire case is not exactly silent when things get hot. Almost all Silverstone cases are way better than average at cooling, but sometimes theories don't work out as well in practice as you might expect - witness the Raven RV03 with the motherboard rotated 90 degrees; the bottom inlet fans needed to run fast enough to push air all the way through the case and the result was too noisy. I've experienced the same problem with the Fortress FT03 Mini - although it's a brilliant design with an unbelievably small footprint, it gets a bit noisy when the graphics card is working hard.
The only inverted mainboard layout (BTX) case with a fan near the graphics card that I can find in today's market is the MicroATX version of the BitFenix Colossus (the MicroATX versions of the Phenom and Prodigy should be much the same). But these only offer a single optical drive and Stereodude's hypothetical construction needs two. Anything with room for two or more optical drives was designed a few years ago when the emphasis was more on keeping the CPU cool. So the graphics card is in the middle and not very close to any case fans.
Something with a side intake fan next to the GPU would be good, but the Silverstone TJ10 is eye-wateringly pricey.
Alternatively, as Ddrueding says, put it in a cupboard. My induction cooktop has twin cooling fans that are enclosed in a cupboard about 1.5m long. I use standoffs to ensure the doors don't quite completely close, but I can't detect any noise 1 meter in front of the cupboard.