I personally would not want to fish a 6" hole even for panfish, unless you are going to drill a second hole right next to it for your sonar. I bought a 8" k-drill this winter, and so far my 20v dewalt hammerdrill has plenty of power for it. The 8" hole has nearly double the surface area (201" versus 113") compared to the 6" hole. This extra surface area really comes into play when the ice gets thick and your hole isn't perfectly vertical.
Last edited by timsirek; 01/03/2017 03:23 PM. Reason: Math break, added text.