Oh, I get it. The first time I read it I thought that the poster was saying that 5D II or 5D III were high megapixel and were unnecessary. I see what was meant now.Also, images from a high MP camera is going to take a lot of harddisk place. Unless you are intending to make large prints or some drastic cropping, running out of space on the hard drive will be the only difference you will probably feel between 5Dmk2 and a high MP cam... IMHO anyway...mRAW, sRAW. Problem solved. You can always downscale resolution, but it's impossible to add resolution beyond the camera's capabilities.
I agree TS-E lenses are a necessity (especially 17mm and 24mm I or II). Full frame is a definite. I'd say a 5D or 5D Mark II will save you a ton of money so you'll be able to buy both FLs. Good tripod and head is also necessary.
Additionally, you could add a used T2i, T3i, T4i or 60D in order to acheive 28mm and 38mm TS lenses with the crop factor (at 18mp; cropping the a FF picture from 5D would be 5MP, 5D II would be 8.2MP).
Except high MP cams don't shoot mRAW or sRAW. At least none that I know of. I'm not counting the 5D3, 5D2, or 1Ds3. The D800 definitely doesn't.
your kindness made me so happy , thanks alot for your advices . and my last question ( i promise ) if i want to take videos ( usually short one ) of architecture for somewhere that still images do not cover the scence , or do not transfer the feel of space .... what do you think i need ? ( i mean extra)If I read what you're asking, is that you probably want to do some slow, smooth panning shots to better 'feel' the space. I have no direct experience with that, but I would think the 17 and 24 TS-E's would be good for it and require a good, smooth pan head (or geared head) on your tripod and with accurate measuring of the level of the mounting plate. Now if you're talking about follow shots or dolly shots much more equipment will be needed (rails, etc).