I have heard ati's latest cards are pretty large and thought I better check before persuing this. I don't have a lot of knowledge about computers so any help would be much appreciated.
Furthermore, he has helped me pick most of the parts, but I'm not sure whether an Intel or AMD processor is a better partnership with these graphics cards. I do alot of 3D rendering too so I do need the best setup to save on time.
Using a ruler on my screen and the picture below, I estimate you will only have 260mm to the HD cage (80mm rear fan measured 17mm, distance to HD cage measured 55mm, (55*80)/17= about 260mm).
As you need about 295mm to fit these GPU's, I would recommend a newer case.
If you are doing a lot of 3d rendering what you really need is a Intel Core i7 CPU and TONS of RAM.
The GPU(s) will have little impact on the rendering time.
Look into a LGA1366 platform with a minimum of 6Gb RAM.
outlw6669 - Last month I did a lot of research and reading about the Intel Core i7 920 cpu and the Intel Core i7 860 cpu. I specifically searched for technical reviews and benchmarks for digital imaging, video processing, and 3D rendering. I thought the 920 would outperform the 860. As it turned out the Intel Core i7 860 is better suited for those types of mainstream graphics applications. Intel was correct when they announced that the new socket 1156 cpu's were intended for mainstream use. They just happen to be okay for games too.
The same thing happened with the ATI Radeon HD 4770 video card early last year. It was introduced as an excellent general purpose video card. It just happened it could handle games fairly well. The results were not spectacular but the card did well. Two of them in Crossfire produced even better results.
The i7 860 is clocked higher stock and turbos higher also.
Defiantly makes sense that it will perform faster.
I was thinking LGA1366 more for the support of future 6+ cored CPU's and the ability to stuff in more RAM.
Either platform should work great for the OP, LGA1156 will probably do it a little cheaper.
The new Lian Li / Lancool Dragon Lord series are mid-tower cases that can handle most long video cards. The lower hard drive cage is mounted sideways. The distance between the rear of the case and the lower drive cage is 290mm which works out to about 11.4 inches.
The top of the line ATI Radeon HD 5970 is over 12 inches long. It will not fit in a typical mid-tower case. It is one of the longest cards made. I don't have any specs yet for the new Nvidia Fermi. It is not even certain when it will be released.
My crystal ball is cracked and does not work. I can't predict what will happen to video card lengths.