Is HD worth the 20% markup over the "regular" radar. I'll have a Garmin 4210 & a 498 on the new boat, now trying to figure out if I NEED radar - I have NO schedules that make me leave the dock - and if I NEED it is the HD worth the bucks ? My eyes have trouble determining the difference in regular & HD TV from across the room, yet all my TV's do the 1080i...