So,

Currently I have an Optimus T phone with the $15/month pre paid UL text/10cents a min plan. It's not that great for me as I'm starting to make calls more often(finally have a girlfriend, lol). I'm hoping to just get the new $30/month plan everyones talking about with UL text/web and 100minutes.

What I'd like to know is, could I buy a non pre-paid phone(such as the One S) for the full price somewhere(wherever is cheapest), and just buy a T-mobile SIM card and pop it in the phone with that plan? Or do I need one of the pre-paid phones T-Mobile offers on their website? I've had the same plan/phone for quite a long time, it needs to be replaced!