Have some Cabela's bucks to spend - time to upgrade fish finder/ GPS. Looks like 7" is the right size - lots more models to choose from than expected, all sounds the same. Which one should I get and why?

Choices:
Lowrance® Elite-7 Ti Medium/High Sonar/GPS Combo
Lowrance® Hook-7 Base Mid/High DownScan Sonar/GPS Combo Combo
Lowrance® Hook-7 Base Mid/High DownScan Sonar/GPS Combo with Navonics+ Mapping
Lowrance® Elite-7 Ti Combos with Navionics+
Lowrance® Hook-7 Mid/High DownScan Nav+ Sonar/GPS Combo