Thanks guys for all the helpful posts. I really appreciate it. I have got my gear, and want to post an update.
After a lot of thought on the matter, i decided to not house by D300 after all, and instead, house my video camera. Don't want to get into all the messy details, but i just decided that for now, i would be happier with video.
Since i already owned a Sony HDR-CX7, all i had to do was house it, get some lights and a wide-angle. I have done that now, my kit arrived yesterday, and i am off to the Philippines this Friday for 10 days.
After pursuing many of the suggestions here, I ended up buying from Fun-In in Taiwan.
I emailed several vendors in Singapore and Hong Kong including the ones mentioned here (although not Andrew), and got no response. I did not contact Japan.
I emailed BackScatter, ReefPhoto, and H20 in the States and got responses from BackScatter and H20. Unfortunately, even with the miserable state of the US Dollar, these vendors simply could not compete on price. Their quotes were 25-30% higher than both quotes out of Taiwan, which amounted to 800 to 1,000 dollars.
I did get a nice and competitive, but awfully slow, response from divervision, and would have pursued them more if they had been more responsive. I will certainly try them in the future.
Sandy at Fun-In was very responsive, offered the best price ($3,000), and was very helpful. She's on Skype, so easy to chat and talk. They promptly ordered the housing for me from Japan, and had everything ready in a week. Payment was made via PayPal, and they delivered the package to a shipping agent i know near the airport outside Taipei and I had everything in hand 48 hours later (Shipping, including all customs/import taxes/VAT, was US$165). A wonderfully smooth transaction.
I really appreciate all the help from all of you.
With video, I hoped to reduce costs, but more importantly, reduce complexity. There just seems to be so many moving parts (figuratively and literally) with DSLR underwater photography. I have such tremendous respect for the photographers who produce all the stunning images we see here. I realize how tricky it can be... especially after reading all the forums on TTL, lens choice/focus, etc. etc. etc. Just in the last couple days, not the mention the last year i been following them...
Anyway, thanks again for your help, and hope to see some of you on the video forums.
So then, what's all this chatter about white balance? (there's always something, huh?)