Need some advice specifically on Garmin Sounders (chartplotter plus sonar).

I am currently running a 24' Albemarle with Raymarine L750 F/F, SL72 radar and RC420 chartplotter. All non-color. I bought the boat in Sept 07 and haven't mastered these yet.

I have used Garmin products for aviation, car and treking for over 15 years. I want to get a Garmin Sounder for the boat to use until I get the hang of the Raymarine equipment. Then it may become a backup unit.

I'd like to stay under $1000. I want to be able to add the various charts depending on where I'm at.

What are you using that works for you and that you like?

Give model specifics.

Thanks

Lar