A desktop HTPC case will be difficult to fit a 8800GTS, much less a Hyper TX. Have you considered a regular mATX gaming case, like the Ultra Microfly. A 8800GTS could possibly be squeezed in there, but I'm a bit afraid about the Hyper TX-2. Unfortunately, the only confirmed case of a n 8800GTS fitting is in a $200 case; I just don't have the info on the other cases, but their size differences are not really that much different.
I've recently built a gaming computer and it is a mid-tower case in my living room. I've decided that I would like to use a desktop HTPC case. I've looked around and it has been hard finding one that will fit all of my components. More specifically, my 8800 GTS and Hyper TX-2 cooler. My budget is fairly limited and I don't need touch screen like I've seen on high end cases.
And another question, how would I reduce computer noise if it is placed within a cabinet? The cabinet has plentiful open space in the rear.