Hi Steve & Linda,
I have been going through old blog posts and came across the series you did on SONAR. This reminded me of the recent update showing the install of a Furuno unit in a new 64. I just wanted to direct you to another manufacturer that you may not be aware of. They’re just across the sound from the folks who make your auto-pilot. http://www.wesmar.com/commercial.html (I don’t work for them in any way, just thought the product looked interesting.) I particularly found the testimony of a sailor who sails the Antarctic for a living compelling. http://www.wesmar.com/pdf/Customer%20Reports/national_geographic_explorer.pdf It could prove to be a decent alternative to Furuno.
At the time we decided on Furuno we felt they had the best product for our needs.