Where to make holes bigger for fans....

Alright, I decided in the near future to make some of my 80mm fans into either 90mm or 120mm. Any sugestions as what to do with what holes and how big to make them???

Here is the case:

I'd probably change the intake into a 120. That one should be easy. If possible, the exhaust and the blowhole should be 120 also(less noise, more or equal airflow). Sometimes there just isn't enough room for 120s so in that situation, go with with 90s. The 2 side should be fine at 80.

I'm assuming that case is acrylic, which can be a difficult material to make clean cuts into. I'm no master machinist, but i would use a hole saw (sharp!!!) on a drill press at a low speed. If you go too fast you'll end up melting the acrylic and it will look like crap. If you can, run water over the cut while doing it. I would avoid a dremel in this situation.

Here is a thread that goes through the same question. Happy modding

Edit: Whoops, i thought u asked how to cut them, lol. Thats what sleep deprivation does to you. I would go with a 120 on the front intake or top blowhole (would make adding a watercooling radiator easy in the future) but that case has a lot of fans already. Case airflow increases make a difference to a point, but then usually just start adding noise. I bet case temps are going to be within a degree or two of ambient even if you didn't upgrade the fans.

I have the tools to cut the holes but I want to make sure I do this right. I am kind of scared of ruining my BRAND NEW CASE, but I want better airflow. If ANYONE knows how to make clean cuts into acrylic PLEASE HELP ME!!!!!!!