Electric blanket in bed? Some clever heating elements in the shelves?
Silence is top priority.
If silence is your goal everywhere on the boat then a diesel heater is out. Diesel heaters come in two flavors: air or hydronic. The air ones don't make much noise, but if that's your criteria, so be it. Generally the heaters are placed in a cockpit locker and the ducts or pipes get routed into the cabin. Hydronic is quieter in the cabin.
Since the heat you have works for the saloon, then get an electric blanket, although you'd have to turn the heat down when you plug the blanket in to avoid tripping the main AC breaker, depending on the loads, especially if you only have a 15A service. With 30A you'd be OK. Do the math.
A fan is a good idea. But you don't like noise. Can't have everything, now can we?
I sailed in SF for 35 years, and while I didn't liveaboard, I sailed and anchored out lots of times during the winter with just a catalytic heater, equivalent to a 1500 watt electric heater. It was cold(er) in the V berth, but bearable, with a good sleeping bag or two or a big duvet. Now that I am on Vancouver Island, it's a lot colder and I have to either curtail my sailing or install a diesel heater. It snowed last night and it's 0C!!! You won't see that where you live.
Our real trawler lamp
http://www.westmarine.com/buy/weems-plath--trawler-lamp--6723563 also made a BIG contribution. Still does. It HAS to be REAL one like the link with that type of burner. A simpler one with just a wick won't do squat.
If you have 30A service you could get another electric heater, but couldn't run you water heater at the same time. Again, do the math on the loads. You shouldn't be running the water heater for any longer than it takes to heat the water anyway. It's becomes a management issue.
Good luck.
