Just know that with the ATV preset, you're bloating DVD content.. NTSC DVD's are encoded at 720x480. For me, its overkill so I use the universal preset instead (don't have a plasma, but the vids looked damn good on a friend's big screen LCD.. not sure of the size, but it was way bigger than my 32" LCD) but you will probably want to encode one with the universal preset, one with the ATV preset, and one or two with custom settings to see which one you prefer.
You may also encode some DVD's with one preset and another DVD using another preset. Since many dramas encoded using the universal preset come out with a smaller file size than they do using the iPod legacy preset, you may not need as much detail as you think, and using the universal preset will be fine, whereas with TV sitcoms, action or animated films, you may want to use the atv preset.