I use 2 9" units, a Garmin Echomap+ 93sv (bow), and a Humminbird Helix 9 MSI G3N (console). I use the included Garmin maps with the 93sv, and have a Navionics+ card in the 'bird. Both are great, but the SI on the 'bird is really something.
The Garmin also runs the Panoptix LiveScope System, which I just got, and am in the process of installing. So if you only buy one unit, get the Garmin if you think you will ever want to try the LS.
"Alive without breath, as cold as death; never thirsty, ever drinking, all in mail never clinking."