I use a HD6450 for a second monitor, and the second monitor happens to be a 19 inch HDTV, Connected to it with an HDMI cable. The text is blurry even at its native res. But when its hooked up to my monitor with HDMI, its perfectly fine, no blurriness or anything. What I was told When you use a PC with HDMI to a HDTV and it dose not natively support PC, The TV will try to enhance the PC's signal causing it to blur. But it will work on Blueray players with HDMI, They are meant to work on TV's like that.
Only way to fix that is to use VGA or if you have to use HDMI with the PCI, you can use this. http://www.amazon.com/Cable-Black-Video-Support-Necessary/dp/B002TUC64W
But it wont work with sound.