First of all, I don't have a 1610 but a 1620. The burst rate with internal drive firmware is 21-22MB/s. This is too slow to support 16X burns.
Changed to external drive firmware (47L9) and the burst rate was raised to 24MB/s. The drive can now burn 16X discs.
I am using a DW1620 in a Prolific PL-3507 case.
Go read the "Big Extermal Case" thread to get much much more details and many people that have reached 16X.