I have 3 boxes:
1) 65" Mits - 1080i component and DVI (same picture quality for each, so component usually)
2) Computer - SVideo to TV card to dedicated 19" monitor.
3) 27" - SVideo switched through receiver.
I have the computer set to letterbox HD images and they are very good to excellent.
The 27" set is set to all full-screen and the PQ is remarkably good considering it is a 25 year old set.