I need some CM690 airflow/cooling advice

I've decided to improve the cooling in my CM690 case (as a graduation gift from me, to me.  ) but there's a few things that I need your help with.

I can either:
A) Replace the stock 120mm fan/add another 120mm fan to my heatsink (http://www.newegg.com/Product/Product.aspx?Item=N82E168...)
Or
B) Replace the giant heatsink and add in another side fan and two fans at the top because they won't fit otherwise. Is there a heatsink out there that is both small(-ish) AND effective? The current heatsink is pretty damn good but I'm wondering if the extra fans will result in better cooling.

I also plan to replace the stock rear and side fans along with adding another one in my drive bays regardless of the above. The case supports up to 140mm for the side and top fans. Do these move much more air than the 120mm ones?

What I would like from you wise computer people is to help me decide which method to go with, answer any questions I may have asked thus far, and recommend some of the most popular 120mm(or 140mm) fans out there. Also, I'm Canadian so if you're going to provide a link to something, make sure they ship here.  

Thanks.