Matt... $1500 is a good price for an installed unit but you obviously can do better if you do it yourself. First questions...
Is this just for weekends & short vacations on the bay or is it for long distance, full time liveaboard use? I will assume the former but the following does not apply if we are dealing with full time cruising. It also assumes you are fairly handy and want the cheapest unit that will do the job.
First...buy the Adler-Barbour Cold machine CU-100 compressor coupled with their VD-150 evaporator/coils and thermostat. Defender has them for about $1k...can't figure out the sailnet deal!...but this is the industry "Camry" ....a standard that works well and is universally fix-able with a low amp draw and high reliability. Perfect for bay cruising.
To install...you need to run you 12V lines from your open 15 amp breaker switch to wherever you are installing the compressor , cut a 1" hole in the ice box for the refrigerant piping, mount the condensor and thermostat in the box. Connect the pre-charged piping at both the condenser and compressor ends, plug the thermostat phone jack into the compressor, fill the whole you cut with putty and make some ice cubes! Really about a 2-3 hour job if you have decent tools and good access points and don't have to do any "customizing" . It is surprisingly easy to save 4-500 bucks by doing it yourself.
Here's the installation manual for your review:
ERPS...great minds think alike. Good thought on the SSCA guy as a possible source.