The newer garmin models are the 1460 and the 3790, these are in the region of 800-1.2K. The more expensive units are smaller, and are meant for people who walk and travel with GPSes.
One thing to understand about GPS is that although the units are different, some of them run the same software. You can find some taiwan GPS units running garmin mobileXT, which is also made by garmin. The difference is that the newer models support 3D and other extra features. Some taiwan units also run Papago and Mapking.
The cheaper garmins about 600-700. about the same as taiwan models.(and maybe slightly more expensive, if you start looking at very cheap taiwan units) Taiwan models have extra features like MP3 and video, but they're not really that great IMO, because it's not running together, you turn on MP3/VIDEO mode, the navigation doesn't work.
AECO units are the original distributor sets, and slightly more expensive. The gray imports also work, but they're not the local versions, and might require some additional things like voices, (if you want to run Malay navigation voice) but those can be added on, and most GPS shops can help you with installing extras.
GPS units also require frequent map updates.
My ASEAN Free GPS Map Project • Index page is a good place to get the latest maps, and reviews of GPS units. Also got dealers from various parts of Malaysia there, so can choose one that allow you to test their display units.
The garmin city navigator has junction view and lane assist, but it's sadly outdated, so most of the time, you'll end up using MFM maps, which has a larger POI database and more up to date maps, especially for rural areas.
There's other options like Papago and the local made GPS unit, but I can't tell you much about them since I never tried them out. I did try papago on a taiwan unit, but driving at 80KMH, the lag from them made me miss turns usually, which was why I ended up with the garmin unit.