We all have our favourites but I settled on a Garmin... a plotter/sonar combo like Jeff but virtually the same unit was available as a sonar. It was on a great deal at the time including charts for the whole UK (perhaps Europe too I forget) such that the unit wasn't that much more than just the electronic charts bought standalone.
The modern version of my Garmin is an Echomap Plus 45DV at £320...
https://www.force4.co.uk/garmin-echo...der-combo.html
You then choose your transducer as an extra cost.
The fishfinder version is £190 inc the transducer...
https://www.force4.co.uk/garmin-stri...ishfinder.html
And a slightly more budget version of the fishfinder at £130 inc transducer...
https://www.force4.co.uk/garmin-stri...ishfinder.html
I have no grumbles about the Garmin so would happily buy that brand again.
Here is a bit about me fitting it, post #19 shows the finished job...
http://www.rib.net/forum/f37/garmin-...tec-69858.html