I put my first DSLR rig together this year. I have a Canon 40D in a Sea & Sea housing with 2 YS-250 strobes, UCLS arms and a Fisheye 48DX LED focus light. I have the ports and focus/zoom gears to support the Tokina 10-17mm and the Canon 10-22mm along with the 60mm and the 100mm macro lenses. Everyone will have their own "best system". What's right for me might not be what your looking for so I will attempt to talk a little about why I made the choices I did so you can have a little more info to make your own choices.
I was changing over from the chemical photography I had done using a series of Nikonos cameras. My motivation to move up to the DSLR came from a request by a developer to use some of my film images in a hotel/condominium project. This architect really liked my stuff and it was just enough of a push to get me started down the digital path. I knew I wanted a system that provided the best image quality and versatility I could reasonably afford. The nikonos system was great for it's day, and can still make some incredible images but you are severely limited in some areas. I wanted my new system to fill those holes.
I surveyed the available camera systems and purchased a 350D a year earlier so I could begin to learn how to deal with the digital world. My decision to go with a Canon was based on the fact that I had a lot of Canon glass from the film days. In retrospect a non issue since I would need all new lenses anyway, but I didn't know that. Sometimes it just comes down to Karma, I was celebrating my 40th year of diving so the 40D seemed like a great choice for my first underwater DSLR. Actually it was positioned technically right in my wheel house. Very good image quailty, big LCD which I love, larger viewfinder, easy controls, etc. and it's not ridiculously expensive. I don't do underwater photography for a living or I might have made a different choice. I give my Nikon friends grief sometimes but in reality either system in the hands of a competent photographer can do amazing things. In retrospect the 40D was a great choice for me. I love what it can do.
The housing was a tougher chioce, I live in the desert SW so there was no place close by to put my hands on the different options. Eric's post from last years DEMA came at a great time for me. He went to the trouble to post images of all the new housings for the 40D that were still to be introduced and saved me a ton of work and travel. All of the folks on Wetpixel were a fantastic resource and helped me immensely. The best thing a potential buyer can do to save some growing pains is spend the time to research the posts here. In the end it came down to the Subal, the Sea & Sea and the Aquatica. The Seatool wasn't released yet and I wanted an all aluminum housing so the Ikelight wasn't on my list. Based on features and price point I choose the Sea & Sea and it's been very impressive so far. The new MDX housings are very nice pieces of gear. Solid, nice locking ports, very well made, with well designed ergonomic controls. The 40D was the first Canon housing for Aquatica and they didn't have the port selection available for Canon lenses at the time I was making my decision. The Subal is a gorgeous tool but I didn't feel I could jusity the additional expense. Again if I was making my living with it I might have made a different choice. On a business trip back east I was able to stop by the great shop of Underwater Photo-Tech in Derry, NH and finally lay my hands on real housings. This cemented my choice and the rest was easy.
The new YS 250's looked perfect for what I wanted to do and they turned out to be even better than I imagined. The miniscule recycle time on the big strobes is very different from my old Nikonos strobes and completely changed the game. Our past experiences always affect our decisions and I'm haunted by the time I was being looped by a manta in the waters off the outer reefs of Belize while I hung there stupidly waiting for the strobe to recycle. Never again, if I can help it. When it comes to light, I want as much as I can carry and control. The well written articles by Berkley White of Backscatter in Monterey came at a great time to help me decide on the strobes. The great guys at Backscatter were a superb help all along this little journey.
I decided on the Fisheye 48DX focus light. This is the LED version with 50,000 hr bulb life and a huge 10 hour burn time on one set of batteries. It's about half the price of the halogen version and uses the same difusers. It puts out plenty of light for the AF sytem of the Canon, a little over half power on it's adjustable output is all I needed. Ryan at Reef Photo was a big help in getting me set up with a small arm that would get the light high enough to get over the dome when I want to use it at night or for CFWA.
All in all I'm extremely happy with the system I've put together. I still have a lot to learn but I'm headed in the right direction. If you'd like to see what kind of images the system can do in the hands of recreational shooters on their first attempt take a look at our web page on Flickr (linked below). I have some old film images up and a new set called digital Bonaire from my first trip with the new rig. The macro shots felt much easier to do with the digital system than the old Nikonos. I found that good wide angle images were harder to get than I expected, I still have a lot to learn. The fish shots with the new system were miles ahead of anything I was able to do before.
One other note, I spent a lot of time reseaching the folks who advertise here on wetpixel and some who don't. In every case I got great, helpful, accurate answers to all my sometimes dumb questions. We are blessed with a group of fantastic people supporting and supplying us with equipment today that previous generations of divers never dreamed of.
So do your research, decide what you want the tools to help you do then use all the great resources at your disposal to find your own treasure.