Question is what depth finder with sonar is the best bang for your buck?

I'm a bit partial but if you haven't looked at Garmin recently, I'd highly suggest it. I've never had a real nice unit but I'm amazed at how clear and easy they are to use. 

Here's some massive schools of shad that were everywhere a couple weeks ago.

 

A couple shots from spots where I picked up fish last week.

 

I have the 93SV, which is cheap for what it is, but you can get much more affordable units that do the same thing that are just smaller.

Your title and question are different.

 

Are you talking down imaging, side imaging or both.

 

Best at the moment IMO are the Garmin 7600xsv series.

 

Best bang for the buck HB Helix

 

Best intermediate screen size Garmin 93sv