I also have a GPSMap 60csx and like it. Choosing a GPS has gotten to be a very complex task today though since there area lot of models. As much as I like the 60csx, its real weakness is the quality of the display, which is 5 or 6 year old technology. The screen is very low resolution - 160x240 pixels - which is pretty bad by today's standards. It can also only show 256 colors which limits the quality of the map display. It's hard to read the screen unless the light is good, and the backlight is too dim (plus it sucks down the battery quickly). This isn't a "deal breaker", but it's a disappointment for what is otherwise a really nicely designed unit.
The 60csx uses the newer technology SiRF GPS chip than the GPSMap 60. The SiRF chipset is much, much better at getting a signal in difficult locations, like heavy forests. I owned three other GPS'es before getting a SiRF based unit, and they would often lose signal (usually at the worst possible time
). However there's a downside to the SiRF chips - they favor getting a signal over accuracy. Usually this isn't a problem but as an example, an older GPS might not get a signal at all in the dense woods, but the SiRF unit might get a signal but show your position 50 feet away from where you really are.
If you want a GPS with topo maps then you will need to stick with either Garmin or Magellan. TomTom makes some really nice units (I recently got one), but no topo maps are available. I haven't used the Magellan topo maps for several years, after selling my Meridian Gold GPS. But at that time I felt the Garmin maps were better. This may have changed since then. Magellan just introduced the Triton series of handheld GPS'es which look
very cool. The top of the line units have touch screens and other advanced features. I'm not sure whether these are even available yet since they're so new and I haven't seen any reviews. But if they deliver on everything they promise then I suspect they'll give Garmin a run for its money and set a new standard.
If your use is primarily for the car with occasional hikes you might consider the Garmin Nuvi 750 or 760. They have built-in batteries which will run the unit for several hours, they will do voice prompts, and can use both topo and city maps. The big plus is the quality of the screens, which are 480x272 pixels (that's more than
3 times the resolution of the 60csx screen). This means you see more of the map, and they also show thousands of colors which makes the map look better.
The downside is that these units are primarily aimed at auto use and are missing many of the "outdoor" menu functions such as a compass, elevation profiles, etc. They also use touchscreen techology, which IMO is a good thing most of the time. It's a lot easier typing things on an on-screen keyboard than using a cursor button for example. The battery is non-removable and won't last as long as a unit like the 60csx so it won't be great for an all day hike. And the ergonomics are not as good as a unit designed for outdoor use. They're also not waterproof.
Happy shopping, hope you find something you like!
So there are some third party applications which run on the TomToms, and some utility programs which let you design your own map color schemes and menu heirarchies.