You could mod the top of the case and put a high cfm fan to exhaust some of the heat.
you could try and replace one of the stock fans (before you do any modding) and see if that drops the temps as well. if it does, then you could purcahse an additional high cfm fan and opt for a pure push system, or positive airflow system, without the need to mod.
If temps drop with one fan by a reasonable amount, then you know that a pure push system may be the best way to go for that particular case.
What are your temps?
Do you care about noise in your fans?
IF you dont care you could get two of these for the +airflow setuphttp://www.newegg.com/Product/Product.aspx?Item=N82E16835185054
You could also try CM sickleflow fans they are rated at 69 cfm, and are pretty quiet. There are other more quiet options that have similar if not better cfm, but not for the price.
If you mod the case you should opt for fan placement on top.