anything less will wear out trying to pull the rest of the train.....
As for the fan location, you could cut a hole in the top of your case and mount a wire cover over it with a couple of screws so the fan on top of a power supply can be accommodated. Otherwise see if you have other areas in the back for fan circulation...there are some made that mount to the open slot holes that pci type cards would use to be screwed to the case (the fan doesn't actually go into the slot, it only uses the back hole mount area). I've used those types in order to pull/push air inside the case to keep things cool. They plug into extra power plugs and are identical to the type you use on the back of a cdrom or harddrive. If you don't have enough of them now, you can buy Y adapters that give you a couple of extras.
I want to change power supply. How does a dual fan mount (specifically with re: to top/bottom fan). My tower doesn't have vents on top, will it mount fan to bottom, or better to go single fan?
By my calculations, I should have close to 300W supply in the system (but was leaning toward a solid 400W). Any thoughts/disagreements?
My current Power Supply Unit - max output 250W (I was/am having frequent shutdown) This seems rather small. I'm running AMD Athlon XP 2800, 120 GB harddrive, 512MB DDR SDRAM, NVIDIA GeForce 4MX Graphics. Notably system has a DVD, and CD-burner.