Good Sonar/GPS combo

Which is the best one in the $500 range?  I've been using a Lowrance Elite-4x, but it's time to get some GPS on my kayak.  I've been looking at the Lowrance Elite-5, but the Garmin models seem nice too.  On a related note, does anyone have an opinion as to Navionics maps versus Garmin maps?

I recently got the Garmin Echomap 50s with the US lakes maps.  Only tried it out on the water for a short while and found the screen very easy to read in bright sunlight with my polarized sun glasses. Menus are easy to navigate and the GPS worked well.
A review of the unit is here:  http://www.boatfishing.co.za/viewtopic.php?f=65&t=1696

I am holding out for the Elite 5 HDI $449

http://www.norcalkayakanglers.com/index.php?topic=48126.0

Comes out next month.