The D2X and IDS Mk II are really serious cameras which take a lot of work to get the best from them. If you don't have any SLR experience then I would think this is real overkill.
The cost of going from having nothing to a full system with these cameras is very high with both the camera and housing being significantly more expensive.
In Uk terms D70 is only ca.£650 whereas D2X is £3300.
The housings are also much more expensive for the D2X and in short supply.
On top of this you need to buy lenses. (Same for both cameras).
A shopping list for Nikon might be:
10.5mm
12-24mm
60mm
105mm
which comes to around £2,000.
And then you need strobes and arms - around £600 each. You will want two.
So total system costs for D70 is probably around £6,000 while for D2X probably hitting around £10,000+
That is a significant difference.
My route has been to buy into the cheaper level camera while getting lenses, ports, strobes etc and then I will probably upgrade housing and camera when the next generation of cameras come along. The total cost of ownership will be less from a cashflow perspective then and hopefully I will have got to the point where I am outgrowing the serious amateur camera and ready for the full pro outfit.
The bottom line is that IMHO unless you are a top level photographer, like Alex, then YOU are the limiting factor not the camera.
I have given examples using Nikon, Canon would be more expensive because the MK II is more expensive than the D2X.
Mark