2*16ner vs. 1*20ger

Sooo! I am still busy planning around! I want to have my 2 16ner out. Now I have looked after strong 16ners and then it occurred to me that you can also install a 20ger TMT. My scans are separated at 2.5KHz, so far a 20ger should play up too. but which one? Because of these you always hear quite little