Sorry for getting arsey, just it's pointless having two threads on the same thing, it just spams up the forums. if you want to come back to the topic, bump your old thread, if it's in the wrong forum, RTM it, and ask nicely for a mod to move it for you.
OT, If I was in your position I'd get it straight in my head as to in which direction air will be moving. The easiest way to do this is with a diagram. A diagram will help us give you advice as to what would be best as well.
You want air to have a nice smooth path, and as I see it, air will move from left to right through your cooler at the moment. I'm assuming that there's only an exhaust to the left of the cooler, and not above, and that the fan on the cooler is blowing towards it. Is that correct? If so, I would leave the hole, as it's only going to interrupt the way that the air is moving. That said, it is worth a try if you have a fan lying around, just sellotape it onto the outside and see what temps do with it on and with it off.
I read your thread about cable ties, pretty as they are, they'll be messing with airflow, if I were you I would do some cable managements, and get as many of your cables as you can tucked away, so that they aren't stopping air from moving inside the main area of your case.
