Re: Radar ?'s
Depends on what you want from the system.
For night time navigation just about any 2-4KW dome system will do. The narrower the horizontal beam width the better resolution you'll get.
If your into fishing and want to see birds, I'd go with a 6 kW unit and an open array. Be prepared to drop some big money if this is the way you want to go.
For general navigation, I like the Furuno 17XX series. They provide good performance in a standalone unit that will run you $1,500 - $2,500.
Garmin, Raymarine and Lowrance, all make radar add-on to go with their chart plotters. You could get a nice 8" Multi-function Display and add a dome to it and still be on budget.