If you can stretch your budget just a tad further ... consider the Helix 8 chirp meaga SI+ G3N. It has all the bells and whistles of the larger units for less bucks.
One of the board sponsors might be able to get you one for close to $1100.
Anything smaller than the 8 doesn't have as much power and don't have as good of transducer. If you are going to invest in one ... spend a little bit more an get the 8... you will be glad you did.
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Looking for the one that makes it all worthwhile.