I always try to fit everything inside the box. I always have intakes at the bottom and exhaust at the top. I try to put the fan before the filter so that the filter will muffle the sound of the fan a little bit. a powerstrip will be able to handle the eletricity no problem..most powerstrips can handle 600-1000w. The DC power supply you'll need to run the fan controlller should look like this - if you hook up fans without a fan controller then you can just scavenge a DC adapter from an old appliance or find one at a thrift shop. A PC powersupply is big and bulky and has alot of unnecessary electronics in it...you also have to 'jumper' it to get it to even start. (they normally won't start unless there's a motherboard attached) I have single pc fans that have been running off phone chargers or old nintendo power supplies for years straight without issues. ..also when setting up the fans/exhaust I try to create a sort of airflow across the bulbs directing the heat towards the exhaust. This usually involves putting the exhaust 'hole' right by the base of the bulb and also having an additional fan blowing air across the bulbs towards the exhaust. I've done the plexi thing in the past..but after the build I'd test the boxes with out the perpetrator and they worked just fine. It really depends on exactly how yer venting is set up but make it so that you can pull the glass/plexi out easily to see if it's even necessary.