You don't mention what your budget is or what exactly you are trying to fix/improve, so I'm going to make some assumptions.
The rear projection gives poor off-axis picture quality (I'm sure that you've noticed). LCDs also have problems with off-axis viewing, so a plasma is what you need.
The newer plasmas work very well in semi-bright conditions. Just get one with an anti-reflective screen (all but the very bottom models have one).
At 7 feet, you would be better off with a 50" set than a 42", so upgrade the size.
I prefer the 1080P sets, but a 720P would be fine at 7 feet distance. Get the 1080P if your budget allows.
You will need at least one HD source. I suggest contacting the cable company and getting a package with some HD. Get a Blu-ray player if your budget allows.
The choice of which plasma manufacturer's set to buy depends upon your personal preference. Any will be good.
Lastly, start watching sports!