SilverBullets is right on with his advice
most people who are very serious about kokanee would never skimp on a finder and on the 1 to 10 seriousness scale (10 being the most serious) I'm at least a 7 even though I run an old entry level humminbird, honestly I've never felt I've needed more than what I have, I can see how deep the fish are and if I get off course at all and close to hanging up on the bottom I can reel up before its too late
I've been laughed at before at the launch with my $80 humminbird, but when I take out and do as good or better I laugh back
you obviously get what you pay for but in my opinion you can compensate with your adaptability to the other factors like speed, scent, changing lures, slight lure depth changes, turns, leader lengths, etc., spend some bigger money if you want to but don't feel like you have to spend hundreds of dollars to get kokanee into the boat