i already have a 998 at stering column i am wanting a good gps and overall good 2d unit up front i have decided on either hds 5 or comparible hummingbird. What i was wandering was the 597 0r 698 0r 797 do these unit also have donut issue like my 998 (figured some of yall diehard hummingbird guys would know). I want a good gps so i can stay over brush without a marker. I would also consider a magelan unit if anyone knows any thing about them.