What I am worried about is that for any graphics card I install in my system, it may bump into the big heatsink or not even fit at all, so even a high-end graphics card is great as long as it fits.
So from the back of my computer to the heatsink, there is exactly 7 inches (or just under). I have plenty of width/depth at about 5.25 inches from the motherboard. However, the height of the card is going to be important. If the graphics card is too long, then the tail end of the card will have to be about 1 inch tall or under. If the card is say 5 or 6 inches long, then I don't think height will matter.
Also, I can't get single cards that occupy two slots since the PCI express x16 is the top slot. Here is a picture of the motherboard/inside of my computer:http://www.flickr.com/photos/lampywilf/2325751519/in/photostream/
The black processor cover is the big problem here. What do you guys think?