... you're getting closer.
hoosier:
[font=바]1. [/font]I mean that Rebreather is my final step in terms of scuba training to meet my interest, scientific research.
Depending what you do in your research, you should probably consider a couple of thhings. Will over the shoulder mounted counterlungs interfere with you tasks, for example. You probably want a HUD so you can monitor your system or at least your pO2 handsfree. The operating depth plays into it, too, as some units are better designs for deeper dives than others. Rich Pyle is famous for his dives to the 'twilight zone' between 200 fsw and 400 fsw, discovering new species. He uses the Cis-Lunar MK5P, a rare, expensive, high end unit build for extreme dives.
Researchers an FL and Mexico (from CA) use PRISM Topaz CCRs for their research, as does the USNPS. One of the PRISM instructors actually specializes in working with researchers. That unit comes with a HUD and an analog secondary display. Very lightweight (47lbs ready to dive) and long scrubber duration (300 min).
The Megalodon has proven to be quite popular and offers an optional HUD on the base electronics or deco integrated electronics that include the HUD but have no secondary display. Very versatile as tanks are mounted onto an aluminum scrubber housing rather than in a case. Easier to travel amd choice of tanks. Same duration as Inspiration (180 min).
[font=바]2. [/font]So, advanced nitrox certification is only one before taking any rebreather training course? I am supposed to take advanced nitrox and DP this summer from TDI
It should be. I took ANDI's CSU training, that was enough for NAUI CCR training.
[font=바]3. [/font]I dont have any clues which rebreather works for me at this moment. My guide line is
[font=바]a. [/font]It must be the most popular CCR
That is without doubt the APD Inspiration. The Classic doesn't have HUD, something to consider. The newer Vision comes with a HUD and offers optional deco integration. Something to consider. Setback is a backlog of around 10 months ... they are popular.
[font=바]b. [/font]It must be the easiest CCR to get the part and maintain anywhere in the world
The easiest CCR to maintain is likely the Sport Kiss, and also one of the easiet to travel with. But it's a manually controlled unit with a wristmounted display only.
APD has the largest dealer base of any rebreather manufacturer, but in most parts of the world they're still few and between. So for parts and remote maintainance/advice I'd go with a company that offers good support and accessability. Jetsam (KISS), Steam Machines (PRISM) and Innerspace (Megalodon) are all well known for that. Innerspace and Steam Machines also offer factory maintainance training for such special needs. The PRISM I know is very easy to maintain. The Meg also looks pretty good in that regard.
[font=바]c. [/font]And then cost.
Inspiration Classic around $7,600 without options (like ADV)
Inspiration Vision around $10,000 with options
PRISM Topaz $7,800 only option is cowling $250 everything else stock
Megalodon APECS II $7,500 without options (like ADV, HUD etc)
Megalodon Shearwater around $10,000 including options (ADV)