Guy, I'm not sure what you mean by cheap...
I have a ten year old Garmin 38 handheld that interfaces with our ST6000 head and ST7000 course computer and linear drive motor. I just installed a Garmin 178C which also interfaces. I plan to use the 178C for primary track and the 38 for backup. Both share the ST6000 head NMEA socket; only one working at a time.One important consideration. The red (+) wire connects to the GPS data in and the blue (-) wire must connect to GPS ground (the manual says GPS data out), otherwise, it will not work. Took me the longest time to work out the bugs, with Raymarine technical assistance that is.The 178C is really slick. I purchased the 32MB data card (half the size of a match book), which will hold two chart regions. At the present time I'm using only one region, which includes 150 charts, all on the data card. This way I don't have to pack around a laptop. All the charts that I need for my cruising grounds are at my finger tips. Plus it has all the tide tables built in.Terry