for your case, i would recommend LCD not becos its better than Plasma but you need to be careful using Plasma and i'm gonna be bold to assume ur parents arent exactly into HT and i'm not sure if you can get them to understand how to prevent IR or burn in...

btw, since your apps only for Astro & DVD...any HD TV also can do...Sony is expensive..samsung should be more affordable...so, i'd go with Samsung.