your best option may be drilling the clear panel. that way you can keep the "clearness", and not have to use a non-clear fan grill
If you want to mount a 120 mm right over the cpu, then you mine as well get a Thermaltake Big Typnoon or something of the like. The big typhoon (I have it, Its keeps my 630 under 30 C when at stock voltage and Idle) Has a 120mm fan right on it, and it is so big that it may come just to the edge of your case anyways (it does on mine). It is top mounted, so all you would have to do would be to drill the holes in the clear panel, and you would have a beastly CPU cooler AND a 120mm fan. Also, the fan that comes with it is designed to be low-airflow/low-noise. And it could be easily replaced with a stronger fan
you can always use a duct to direct the flow from the fan directly (or closer to) the heatsink. I'm sure you can find some 12cm clear pipe SOMEWHERE. and if you cant, you can always get a clear sheet and wrap it to make a tube. Be careful when ducting, however, because it can get in the way of airflow from other places of the case, and make your case hotter overall.
Creating a blowhole in the sidepanel is a good idea. But, to be clearer on your cooling, what other fans are you using in your system (intake/outtake) and where are they located? It is just as important to have a good directional airstream as it is to have any airflow at all.
I have a 120mm fan at the front bottom of the case, a 80mm on the right side cooling HDD in the front, a 80mm bottom left corner of the side panel (over the PCI slots).
Out going I have the two fan power supply and a dual 80mm setup near the MB connectors.
Now the 80mm over the PCI is close but not close. Temps are rising outside and my CPU is getting to warm.
I could always buy better 80mm fans but I really like the idea of swamping my CPU with a 120mm over head, not to mention taking weight off the HS.
Like a die hard techie I was thinking over kill but may just be I am just lost.
My setup includes:
AMD 64 3200+ Venice ( not overclock but will be after them temps drop)
MSI K8N Noe2 Plat
2x512MB Hynix BT-D43
ATI x800 XT AIW
2x Seagate 7200.10 16MB 320GB
And some other junk.
If you are gonna put a 120mm intake for your cpu that will leave you with
[*:baf587376d]2 x 120mm and 2 x 80mm intake fans
[*:baf587376d]2 x 80mm and 2 PSU exhaust fans
Are the two PSU fans independant (i.e. two side by side), or is one on the bottom drawing air into the PSU and one on the rear expelling it?
If it is the latter then thats a total of three exhaust fans, all of which are around 80mm. You'll prolly want to find the CFM info on all the fans so you can get a grasp on whether or not you're going to have pressure problems once you install that 120mm. If so, a blowhole up top might relieve the pressure.
IMO you got enough airflow through the case. IF you are actually having problems with heat, then consider Thermaltake Big Typhoon as an alternative. it's abit pricy, but dont think you can go wrong with a 120mm fan on cpu heatsink
Annother possibility is getting a 250mm fan and putting it on the side instead of the 120mm. It would be kinda tricky, but it wold look cool as hell, and cool your entire computer. I know you can buy case side panels with the fans built in for select cases, however i doubt yours is one of them. You could always buy one of the side panels, cut out the fan, and find a way to mount it to your case.
You might even be able to find a clear one, which would look great with some lights behind it.
Just an idea. It might be kinda pricy, but it would look REALLY REALLY REALLY cool, and your mobo would be cool too.