Help me buy a new TV... please.

It seems my TV is no longer fulfilling its role adequately enough. When it comes time to play certain video games, particularly those with small text, I can’t read it on my fuzzy, non-HD screen. Also, my TV is huge and heats up my rather snug living room too much.

So what should I buy?

I’d like a TV that will be able to showcase the XBOX 360’s graphics to their full potential. My boyfriend feels like there is lag between the TV and the game system. I’d like to be able to watch hockey and follow the puck. I’d like it to be around 40" and not expel all the heat in the universe. I mean, it’s coming into Spring now and I don’t want to roast while watching the evening news.

Unfortunately, I don’t know that much about TVs. I don’t know what questions I should be asking when talking to the salespeople. The whole true-HD question has me a bit confused. I’m not even that sure what a decent price is. What do you know, Straight Dope universe?