Display Squished with AMD Catalyst on Seiki HDTV

I recently built a new desktop, and my gpu is the AMD Radeon HD 7870 (Gigabyte). I currently have only VGA and HDMI cables, and the 7870 doesn't have a VGA-out. So, I have been using HDMI, which works on Linux (because it uses the "Gallium on llvmpipe" software driver) except until I install the AMD drivers and CCC. I also installed windows alongside it, and it has the same problem from the get-go, before and after I install CCC. I am using a Seiki SE241TS HDTV as my monitor, and it seems to me that the AMD driver wants to treat it as a square TV, so it squishes the output. I have tried changing as many options as I can, and using all resolutions possible, within CCC, but cannot fix it. Changing Overscan/Underscan (which I've found is the solution for many people who have had simply a shrunken output, not squished) helps nothing because there isn't a black border on the top and bottom, it is only huge ones on the sides. I could buy a DVI cable (which may work), but I still think this problem shouldn't happen and should have some sort of resolution besides ditching HDMI. Thoughts?