How big do you wanna go and what's your budget? I like humminbird for the mapping, but Lowrance has a nice product too. Raymarine is starting to get quite a following and Garmin seems to be getting back into the fishfinder business with some new technology as well.
In the humminbird line, if I was going to update the electronics on my boat today, I'd probably put an Onix 8 in the dash and a Helix 7 at the bow................