Chewy,

How much you need to spend, and what kind of bells and whistles you'll want, will depend on what you want the unit to do.

As far as just 'depth' goes, then just about any sonar unit out of the toy class will do that for you.

If you really want to learn to use the sonar to 'see' stuff under you, that is a different story.

I personally do not like Hummingbird Sonar units. Too much 'processing' of the signal without user control makes them, in my experience, unreliable. I have heard that they are getting 'better', but once burned, twice shy. They 'lost' my business years ago, and I'll not go back.

Lowrance makes the best, Bottom Line is great, as are Garmin and Apelco (they make sonar for the US Navy, so they know what it is). Eagle is made by Lowrance, again a great unit for the price.

The 'key' to sonar performance in the lower end (say under $1,000), is vertical pixel count. The higher the pixel count, the more acurately the sonar signal can be interpreted. This enhances things like target separation which allows multiple targets to show separately.

If you really want to be able to 'use' a sonar unit to help you find structure, cover, and even fish, you have to get one that allows you to set the controls manually. If you turn off the 'little fishys' (they aren't fish, by the way), you can actually see and learn to interpret the sonar signal returns that your screen can show you.

With a 'decent' sonar properly adjusted you can accurately find breaks on structure, what cover there is, individual fish, the thermocline (or lack of one), schools of baitfish, even individual shad(if you are paying attention and know what that looks like).

Too many folks don't take the time to undersand what sonar is and how it works. They look at the 'picture' on the screen of their unit, see all those little fishy symbols and what looks like sticks and rocks, and actually believe that they are 'seeing' a 'picture' of what is under them.

Sadly, this isn't the case.

Good Luck!

Buddy