Hey Hunter:

The watts of power doesn't affect how good your display is but the pixel count definitely does. Since I've started using a color unit (HB 797c2 SI) I've learned to appreciate color and wouldn't want to go back to grayscale.

I would recommend getting the largest screen with the highest pixel count you can afford. You'll end up with more watts of power than you really need but that's not what makes the better units more expensive.

You'll want a GPS for crappie fishing but you can get a separate hand-held unit like a Garmin Map76 or Map76Cx (color) and use it in a marine mount with a power supply. With a handheld unit you can take it in another boat, out on the bank and use it for hiking, hunting or driving, etc. Also by having a separate GPS you can devote all of the screen on your graph to sonar and not have to switch back and forth from sonar to GPS.