There are a couple of LittleBear84 mad fan pics of possible locations of fans in the XPS 8930 case.
In the upper intake front location, if you remove the upper HDD bracket you can place a fan there. You can go to the extreme of drilling mounting holes for 120mm fans in the front of the chassis there but you can certainly use some advanced mounting tape to mount the fan in that location inside the chassis. Full size 120mm x120mm x 25mm fan will fit.
In the lower front intake area, you can certainly install a fan using 546insp methods. However, there is a mounting location at the XPS 8930 front intake for a Aurora R5/R6/R7 fan bracket that snaps in. The XPS 8930 shares the same chassis with the current Aurora. That would be the easiest way to put a fan there....just change the fan out if you want to put a different fan in that bracket.