See, Rick has kind of hit the nail on the head. Other forums I belong to, the guys and occasional gal will jump in and give ideas, thoughts, real world experience, alternative ideas...and it is a discussion, often with a good laugh here and there. There often IS more than one way to skin a cat. Here there seems to often be some bitterness or vitriol mixed in, and I'm not sure I understand the reason(s).
To me this is a great place to share ideas and info. That's why I threw in the post about brightness on LEDs I've found. It took me some time to gather that info, and I didn't see it posted anywhere else so I thought I'd share it.
I have 3 breakers for cabin lights, so for me its an easy add on to change them to another power supply. I'm in the same boat that obthomas is...living aboard. But I don't understand your concern about having the lights on ac current. If you are like me, you are hooked to dock power 95% of the time. A weekend cruise is the only time you'd need conversion power....and your inverter will take care of that. While running engines the batteries wont even notice that draw. Sitting at anchor I IMAGINE that eventually these lights MIGHT draw enough juice through your inverter to require your genset for a recharge. But you are going to need your genset for air conditioning or your fridge far more quickly than the lights pulling juice through the inverter.
Another thought is that if you are a live aboard...and running your lights 7 days a week dockside on dc...your batteries are constantly in a state of discharge, with the inverter switching on when they reach a given point of discharge to bring them back, over and over. Is this a concern to battery life over the years? I'm no expert and maybe it doesn't, but I wonder. Its a small drain, but still there. Imagine having BIG appliances like refrigerators running through dc all the time. Nah...we switch those over to ac when at all possible dockside.
The buck converters (dc to dc) also sounded like a good way to go, and I mentioned them in my original post too. BUT, at 3 amps each they wont for example power 5 meters worth of those new 5630 strip lights. They have 5 amp ones as well I believe, but those would still fall short. According to what I found 5 meters worth of strip 5630 will draw anywhere from 6-10 amps. Sounds like a lot, but its still only the equivalent of a 75W to 100W single incandescent bulb in power draw, but with 5000-6500 worth of Lumens over that 16 feet of strip light which is the equivalent of 3-4 of those same 100W incandescent bulbs in light output!
I am going to order one of those 5M rolls of 5630 warm white (waterproof just because its a boat) for my salon with connectors and cut it up and install it with a dimmer (the seller replied to me and said the 5630 is all dimmable). I figure I may not always need it that bright, but at least I'll have the option.