No problem, but 32gb (another 16gb) would likely be wasted money. Utilizing 32gb of memory would be hard to do. Not impossible or anything, just something that's likely not necessary.
16gb is the sweet spot.
So I checked the speed my RAM is running on the current config.. it's running at 3200mhz.. I haven't tested that 1st and 3rd dimm slot yet though.. didn't have the time yet..