In-store can be misleading. They generally use shitty video distribution systems out of the ark, which can make it difficult to tell what really looks good. Check out
avforums for advice / reviews and deals. Personally, I'd go "FullHD" (1920x1080 aka. 1080p) if possible, especially if you're hooking up to a PC or future BD player via HDMI primarily for movies, as you will get the benefit of being able to natively reproduce the source resolution on your display. "HD ready" is generally a by-word for 720p (1280x720) screens, although they are usually more likely to be 1336x768 or something. Ignore anyone who tells you to buy an expensive cable for consumer-grade digital interconnects - it's only even slightly relevant for analog cables (eg, speakers).
My advice would be to get the best branded 1080 LCD screen you can within your budget - there are
good review sites around to can sanity check your shortlist. Since you're after a panel for films, 24p is probably more desirable than 100hz+ support and of course good colour reproduction / black levels. Latency (response time) is more relevant to live action / sports / games - decent current gen displays are unlikely to let you down in this department, imo.
Finally, don't watch TV. It's 99% shit and horrible quality, to boot. If you want to watch TV buy a second hand CRT, it'll be more forgiving of the horrible compression artefacts.