I really like the Lowrance HDS Gen 2 touch. I have the 12" and it is great for using split screen Sonar / Chart

However, in regards to Sonar most units are restricted by the junk transducer that comes with a bundle. My advice is to get a unit without a transducer and buy a decent transducer, you won't regret it and it is the best $ you will spend on the system.

I just got the B21 and it is heads and shoulders above the Lowrance bundled transducer.

-Matt