I use a garmin 60csx - thinking about upgrading to one with a larger screen. The 60csx' still go for good money on ebay, and the discontinued waterproof 500's and 550's can be found cheap on ebay. Anyone upgraded to one of those? Is it an upgrade? I'm not sure if I'd lose any functionality, but a bigger screen would be great for reading maps. Any other larger screened GPS' to look into?