Replacing PSU; Fan Size an Issue?

[Palador]

Hi, there. I have a PC that I've been wanting to upgrade for some time now. The country I live in, it's very hard to find any good parts, but my brother should be travelling to the States soon and I was hoping he could collect a couple of things for me. I'm going to upgrade my RAM and hopefully get an SSD and possibly another HDD as well. However, with my current PSU is not that great. It says "Maxtron Max-400W" on it, and the case apparently is also Maxtron, but I haven't found Maxtron anywhere online for either cases or PSUs. 😛
I kind of doubt the strength of the PSU as sometimes when I do such things as Rendering videos or Hardcore gaming, the keyboard will stop working and sometimes the mouse too. Not sure if this is a PSU-related problem or not though.
In any case, I will probably need to replace my PSU. I think 500W should be good enough for me, but most of the 500W PSUs I've found that are 80+ Bronze or so, have 120mm fans. My current PSU is 88mm (I think), and is mounted at the top of the case, blowing out the backside. The top of the case is closed, so if I put a PSU with a 120mm fan, it would just be blowing at the top of the case, or into it. I don't know much about PSUs, but I suppose that is not a good thing?
I'm not sure what is the best option for me to take?
I hope this was clear enough.

 

[Pondering]

A 120 mm PSU fan would be pulling air out of the case same as the 88 mm. The fan would face down if the PSU is mounted at the top of the case.

It is normal during heavy use such as rendering or gaming at high resolutions.

 

[zhihao50]

one extra tip. make sure he test the equipments before bring it back to make sure it works. Had to return a faulty psu because of the fan in it grinds and produce really annoying sharp noises. Would not be convenient if you have to return it to the state.

 

[Palador]

A 120 mm PSU fan would be pulling air out of the case same as the 88 mm. The fan would face down if the PSU is mounted at the top of the case.

But it would be pulling air out of the case and into the PSU or would the air escape out the back as well?
Is it possible to test equipment bought on Amazon and return if it doesn't work? Or is it on a case-by-case basis? I suppose it's safer to buy from a site like newegg?
Thank you for your quick answers.

 

[zhihao50]

the fan will pull air from the case into the psu and out the back in a typical configuration see this article. 3rd last picture
http://www.tomshardware.com/reviews/cooling-airflow-heatsink,3053-4.html

 

[Palador]

Thanks so much. I wish I had seen that earlier. Being in a hot country where the temperature is typically 30 C, I suppose I should think about getting a new case for a bottom-mounted PSU in the future. I'll look into prices.