If you are looking at the garmin 740, then I HIGHLY suggest you take a gander at the new simrad NSS. Same footprint, will fit the EXACT same size hole, same price, supports networking and a LOT of other features as well.
And if you want to mix/match the B&G Zeus will connect to it and that is a REALLY amazing plotter for a sailboat.
I'd also suggest waiting a bit, and checking the new raymarine, it looks quite interesting. You could do that and an ipad via wifi direct to the ray as backup, would likely be the least expensive route.
exciting times for nerds!