If you plan on getting Direct TV at some point, their HD package broadcasts at 1080i. This signal is a significant improvement over what you are currently seeing. I had a 36" Sony as well and can tell you that the 50" Samsung I have blows it away at 1080i. These sets are currently very affordable, so I would at least reach for the next rung up. BTW, you will be very unhappy looking at standard cable with one of these sets as the picture will look very soft and dull. If your goal is to keep basic cable, I would advise you to just keep your existing set. Off the air HD is free however. Just invest in a decent antenna and watch local channels in HD.
what do i really need 1080p for?
if my only intention of getting a plasma/or lcd is to buy a new tv, that can accept the high def signal in the future, what do i need a 1080p tv for? arent they only really useful if using a blue-ray type source? my intention is to NOT use this as part of home theater , or even to watch dvds..simply watch cable tv. that being said...looking for 46" isnt plasma the way to go? ive got a sony 36" Wega XBR and not much rivals that...so whatever i get needs to outperform it. And 720p of course is way less coin.