my small cab/console that holds large denon avr, dvd, cd, and cable box has a fan that runs 24/7, yep, all the time. not exactly "eco" friendly but i opted to simplify so no fancy temp controllers, no on/off temp switches, has been running 24/7 since about 2003, but one day i might build myself a nifty PWM fan controller, etc. its a 3" 120vac fan (used in military grade electronic gear) that if given full 120v the thing moves a lot of air and is fairly noisy, so i slowed it down with two power resistors. the fan speed is low and basically whisper quiet, but it moves air. fan is mounted inside the cab in upper-left most corner and it pushes air out. the cab itself has doors on the front which do not close air tight so the fan pulls air from the front doors and then up and out. when the avr is up on power the air coming out does get warmer.
the thing to remember is that is is ok for devices to run warm/hot as long as the temp does not exceed its operating specs, etc . having just a low cfm fan to help pull cool air over the devices is a good thing, etc. too much cfm is not good as that just makes noise and will pull in more dirt, etc.
another reason not discussed is fan specs. push/pull designs mean the fan(s) will have different operating environment. as example, push-in means the fans will be operating at almost the temp of "in" air, while a pull-out means the fans will be operating at almost the temp of the hot air being pulled out, etc. fan bearing life (MTBF) and electrical efficiency may be significantly different for the two designs, etc. and to note, turning fans on/off is what kills them.
irfan has it correct, you definitely want the exit up high because heat rises. this is why placing fan up high and moving hot out makes more sense because most cabs are not sealed, there is essentially no well defined "intake". holes in the cab for wires, space around doors, etc, serve as the "intake". if you push/pull air into the cab then the air flow will not be as ideal since now you are essentially trying to move hot rising air against its natural flow pattern (up), etc. and caution, having a big gaping hole in the rear on one side with fan up high on the other side may not be doing anything for your device, the air simply enters the back on one side and goes out the other, be sure you create a flow path that allows cool air to traverse the device(s).
my vote is to always push/pull hot air out and mount fan as high as possible in the cab, and on the side that makes most heat (perhaps multi fans if the cab is multi chambered and has little cross flow between, etc)