Monty...depends on what you want to accomplish and where you plan on going. My buddy Karl has a full radar/chartplotter on his powerquest. Its the coolest system i've ever seen and helped instal! The thing can track 16 different object and alert you if you are on a collision course with any of them!!!! Now his is all a bit overboard but if you know him its nothing new!
I'd say if you were gonna stick around here inthe great lakes and dont plan on making any super late night crossings then a good GPS with maybe a chart plotter would be about all you need.
There has only been one time out on lake michigan that i could have used a radar....and that was coming back form Miluwakee at about midnight and a fog hit us....couldnt see infront of the boat....took us about 2 1/2 hours to get from Racine to Zion!!!