The front fan is only a single 200mm and I do not think that it has the optional mounts for multiple smaller fans...only the top, side and bottom do. The front fan is sandwiched between the case and the drive rack in a fashion that just replacing it would be a task. It should be understood that none of my temps are problems, therefore I'm not willing to do anything drastic or costly. I bought the side fan as an experiment, but it seems that experiment failed. At most, I might dual 120mm fans on the side panel, if the temps do become a problem, but if I'm right about the 200mm fan causing the higher temps because of their obstruction to airflow, I doubt that dual 120mm fans would fare any better. While they would expose a smaller profile to the airflow, they are also square, rather than round, like the 200mm, and would produce more drag.
I have considered putting Lian Li rollers on the case, like I have done with my other computer, which would raise the case ~1 1/2" off the stand, but haven't because of the stand itself (it would be too easy for it to roll off, even though it does have a wheel lock). Of course, even on the bottom, it would be an obstruction to airflow, but I doubt as much as on the side.
EDIT: Hmm, a curious thought popped into my head. Even though I would not mount the fan externally on the side, if I had Lian Li rollers, I think there would be room to mount it externally on the bottom, but then the fan would probably not have any better clearance than mounted internally without the rollers.
EDIT 2: Another odd thought...what would happen if I mounted the fan externally on top, having two fans mounted one over the other? I thought about this because I made a DIY shelf (which sits over the blowhole) that would hide it somewhat, being less of an eyesore.