Personally, if I were going to do it today, I'd be taking a serious look at Garmin's new stuff, where, with a single, configurable display you can have depth, speed though water, all your wind data (real and apparent speed and direction), water temp, air temp, barometric pressure (I believe). Will integrate cleanly with your GPS and I believe will display (some?) GPS data.
We currently have ST60+ knot meter and depth sounder. They work well and we're happy with them.