I'll chip in with my 2 cents also. I have followed the advice of Jerry & darryl, and it has paid off. I am a humminbird man. I haven't made the jump to color displays, but I own a matrix 17, and a 535. the resolution on these 2 units are very similar. I also have a lowrance h20 gps. the 2 depthfinders that I use, I have the 535 on the back, & the matrix 17 on the front. This gives me the option of watching depth changes, & the gps while I'm steering my boat (tiller handle), & then when I'm up front fishing, I can keep up with the same on the front finder. to me, it's very advantageous to have 2 sets of "eyes" under the water for when you are in both positions. if your depth finder has a swivel on it & it's positioned in the middle, you could go with one. So, the other consideration would be what type of boat will you be using. you can get 2 depth finders @ $150-$200, a hand held gps for $200-300, so you can do that, or spend 700-2000 on a big display color unit. The humminbirds that I have owned are great, easy to adjust your setup, sensitivity, alarms, depth (if you have the sensor on the trolling motor. Also, there is a member here, humminbird greg (i think that's his screen name) that can give you more pointers. You've come to the right place for some answers though. the other consideration is how much will you really be fishing. All things to consider, but you should be able to get at least a decent finder for $200-$250.