I have a little bit of insight on this issue, I have a Sony 40 inch LCD 1080P tv, and have had it over 2 years now.
The first thing after reading your post is that I would recommend getting the newest available technology, meaning 1080p. When I was shopping for a big screen tv over two years ago, I was looking at the 42" Panasonic plasma tv that only ran at 1080i (which is not as good of a picture as 1080p). I initially thought that 1080i was good enough for me and that I wasn't interested in 1080p, but a friend of mine convinced me to go with the 1080p, because you don't want to waste money on a tv that is not ready for BluRay. And if you're anything like me, once you get a big screen TV, you get addicted, and you'll eventually want BluRay. The prices are dropping severely on BluRay players, so I will be picking one up in the near future.
Also, my cable box can do 1080i (at least my cable company says that it can do 1080i), so you may want to check and find out.
I never understood when people said that on a larger tv (like a 50") that you do not need anything over 720p. My thinking is that the larger the screen, the clearer the image should be, meaning that you would need a higher resolution, since you can see every detail clearly. I can understand someone saying that you don't need more than 720p on a smaller tv (such as a 32"), since it is a smaller screen area, but I don't understand the reverse; a bigger display area, IMO, should be displaying the best possible resolution available, since you can see all the detail easier. I could be wrong in this.
For the HD picture, you DO NOT have to spend a lot of money on an HDMI cable. You can go to a site like
www.tigerdirect.com and get a Cables to Go HDMI cable for less than $20.00. That's what I did, and the cable works fine for me. Also, if your TV has Component inputs (2 audio and 3 video inputs), your cable company may give you those cables for free with your cable box. Mine did, and it was extremely helpful. I see no differencce between the component input cables and an HDMI cable.
Personally, I would not buy a plasma tv, I would highly recommend an LCD. I know of too many people that have had issues with Plasma. Granted,they were all Panasonic Plasmas, but I would highly recommend a Sony or Sharp LCD. But, that's up to you and how much you want to spend. Others may have different opinions here, but this is just my experience and my opinion. You may want to do some research (apologies if you already have), because both technologies have their pulses and minuses.
