HTPC Help

Hi,

Ive just put together an htpc the specs are as follows:

3.2 Ghz
160 GB HDD
1 GB Ram
Leadtek A350 5900xt

I use it on a samsung 32" LCD HD ready panel.

When I use the normal D-sub cabel the graphics and picture
look awesome. But I bought a DVI to HDMI cable to get better
picture quality and it just looks terrible. It cant display the right resolutions and looks hazy and fuzzy.......

Can someone please help me, is it the Graphics card? I tried my other pc as well and that has a x1800xt, it displays the resolutions but it is not as clear as the d-sub. With HDTV what resolutions should I use. The panel
supports up to 1360x768. It is capable of 1080i......

I'm thing of upgrading the graphics card, if I do what should I go for
as it is an AGP system, I'd like to be able to play some games as well.

My options are:

Sapphire radeon 9800se AIW 128 MB
Sapphire radeon X800
Sapphire radeon X800gt
Sapphire radeon x800xt

Please help.

Thank you