Without a bunch of hacking which is beyond the average guy the only map products you can install in the 60CSX are Garmin MapSource Products. Map Source U.S. Topo 2008 covers the U.S. mainland, Alaska, and Hawaii.
The best deal I have seen recently is at Wal Mart
http://www.walmart.com/ip/MapSource-TOPO-U.S.-Mac-Windows-DVD-for-Garmin-GPS/10740713The current Wal Mart price is $74.00 no idea how long that will last.
I recommend the DVD software rather than the pre-load memory chip. Once you have loaded the software on to your computer you can use the map tool using your mouse and a click to select areas you want to store on your device. You create a map set which you can transfer from your computer to the memory chip while in you gps or in a card reader on your computer. A SD adapter comes with the micro SD chip and works with most current PC units.
http://www8.garmin.com/cartography/AboutCart.htmlCity Navigator will work in your unit. I have both US Topo and City Navigator installed in my 76Cx. US Topo does not have a lock code, City Navigator does. City Navigator can only be used on one Garmin gps unit.
http://www8.garmin.com/specs/mapsource.pdfLook at this which gives you a hint on how to create a mapset and transfer it to your unit. Metro Guide and US Topo work in the same manner.