Originally Posted by Flewis 
It shouldnt matter what way up the psu is as far as performance goes. There shouldnt be any dust in your case to start with tbh. Fit some dust covers to your intake fans and you wont have any problems. Dont buy another psu, not necessary.
My room's always dusty somehow and it does get a bit dusty in my case... got 3 x 120mm intake fans and they seem to hoover it up. Not too bad cleaning the case every now and again with compressed air, but I'm not sure about inside a PSU...... I know that dust can cause shorts as well, and with the fan being on top of the PSU, it seems like it would be completely open to dust.
