You really are asking a question that you already know the answer to...
It's a good question, but you see your issue - do you want more size and will you be watching more stuff in 4x3 or 16x9. Do you want your new TV to be compatible when it is twelve years old like your current TV? Do you want to be able to enjoy HD programming in it's native 16x9 aspect?
I run both a plasma, for daily watching, and a front projector, for night time movies and HD broadcasts and I like that I can simply split the video out of my receiver into the two locations and have them be identical. That's a real plus for me.
Now, is that right for you? Well, armed with the questions above - then the answer is up to you to decide.
On a side note... Why not a rear screen TV? They aren't terribly expenisve and you can get a 45" wide screen for about as much as any direct view HD 16x9 television I believe. Okay, I haven't priced them out, but 16x9 HD rear projection CRT televisions are in the sub $1,200.00 range for a few and are 40-52 inches. That's a pretty nice bang for the buck for your daily viewer.