I just picked up a rack tuner to go with my head so now I need a rack case to fit it all in place. Both units will take up 3 rack spaces but I was wondering if I should invest in a 4RU case to have a gap between the amp and the tuner for the sake of ventilation? For the record, I'm using an SWR Bass 350 head which has some sort of vent holes on the top of it (whether or not that directly impacts circulation I'm not sure). On that note, if I were to one day chuck in a rack preamp or wireless system in that gap, would I risk overheating the equipment at all? As you can probably tell, I'm new to rack case setups. Thanks!