... by the way, swtiching your video card to an 8800 GT will not give you any better display quality. It WILL give you much better video performance ... so if the reason you're thinking of switching is to have better frame rates on games, etc. then it makes sense. But if you're simply trying to improve the quality of the displayed image, it will NOT do that. To get a better image on a TV-based display, you need to get a 1080P television.
But remember that a large TV will NOT have as good a picture as a large MONITOR. There's a major difference in the # of pixels. Basically, a 1080P HDTV has resolution the same as a 24" monitor [It's slightly different, since monitors use a 16:10 aspect ratio and HDTVs use 16:9 ... but it's the same pixel density]. So using an HDTV is, from one perspective, simply "magnifying" a 24" display to whatever size your TV is. But larger monitors have a higher pixel density --> for example, a 30" monitor has 1.98 times as many pixels as a 1080P HDTV. So, for example, if you compare a 42" HDTV to a 30" monitor, the HDTV has 84% more screen area; but only 51% as many pixels -- in other words, the monitor has 3.63 times as many pixels/sq inch as the HDTV, so it will have a MUCH sharper picture.
... and those calculations are for a 1080P TV. A 720P TV (like yours) has roughly 1/2 as many pixels as a 1080P set [50.59% to be accurate]. So using the same 42" TV vs 30" monitor comparison, the monitor would have over 7 times as many pixels/sq inch !!
