What could I do to optimise this system?

That means eastern European (or weird sleep habits). I'm from Germany.

my 2p, 2 front in takes, something optimized for airflow, not air pressure, get a big cooler for your cpu and a fan on the back to take the air out of that, ie. be in line with its fans. take the 140 at the top out, and put a dust cover over it, natural convection paired with the positive air pressure will force warm out anyway, but you dont want something messing with the air flow around your cpu cooler..

also, if you know someone with a 3d printer, or your a bit handy, take a look at the puget systems tour on barnacles channel, look at the fan bracket in the bottom that points a 120mm fan straight at the intake of the gpu. knowing 290x's run hot that would help aswell..

This sounds similar.

Thanks a lot for all of the help, really appreciate it :)