Actually I figured out the problem.
First problem is with Panasonic HDTV and ati drivers for linux. Somehow, ati thinks that my HDTV is a projector so it does not allow me to adjust many parameters (they are not in the gui). One of these parameter is underscan/overscan slider bar I guess. Because I could not find it where it was supposed to be. I have seen a couple of threads on google regarding this issue and I assume it is not resolved yet.
Also, when I use xrandr, I can not see HDMI as an option on the connected outputs. I believe that this is a problem with drivers as well.
as root to resolve the issue. You can adjust the 0 parameter in the end according to your needs. Also, you may need to restart (restart xdm, modprobe module etc...) after this command to see the effects.
About the underscan in grub menus, I guess it is a KMS related issue. I did not bother to resolve this as it does not hurt much.
I hope someone will find these information useful.