One of my next upgrades is Perfect Pass, if you don't have it. And a GArmin GPS 596S since it covers depth finder, shallow alarms, and XM radar weather it will be a neat function for the boat.
Of course there is the LED speaker rings and underwater lights and custom plumbed ballast system if you want also.
When I was a child, I used to talk as a child, think as a child, reason as a child; when I became a man, I put aside childish things.
1 Corinthians Chapter 13 - 11