depends how close to the TV you’ll be sitting, contrast ratios vary a lot by manufacturers, so I can’t help you there, other than the higher the better
If youre asking the question, you probably wont notice the difference between 1080P and 1080i, assuming all else is equal. Seriously.
Watching standrd tv channels, theres not going to be jack difference, its all in how the tv handles the signal. But playing BD’s, you can absolutely notice the difference. Its obvious to some, and others it can take a while to figgure out what theyre looking for.
But basically, get a tv you can afford. If you like it, thats all that matters. Just remember that those super cheap tv’s are super cheap for a reason, they almost always look terrible. And from people i know purchasing them, two different cheapo brand tvs failed within months or purchasing.
I personally would be more concerned with the 120hz screens. I saw the new one and think its a lot better than the standard hdtv.
If you want to future proof, IMO you should go all out and just put the money up front. Take advantage of the shitty economy and take a promotion 0% interest for 24 months and get a better one if you are hooking useful stuff up to it. Don’t be someone with a 50" 1080p TV and use non HD service.