At 46", your choice of premium plasma screens is limited to one - the GT30 as others here have said. My advice would be to see if the space you're intending to fit the screen into can accomodate an extra 4" because that is when the choice really does get interesting.
I've got the 50GT30 after auditioning a few screens, but it really was a very, very close run thing. I nearly plumped for the Samsung 51D8000 and I would definitely recommend auditioning both it and D6900 if you can get away with a slightly bigger screen. The 50GT30 pipped it for me because I watch it in a fairly dim room, where that slightly deeper black level comes into play, and because I got a very good deal. But if your living room has quite a lot of light, the Samsungs do offer the advantage of a brighter picture. Also, SD scaling on the D8000 is excellent by virtue of the fact that they use the same in-house Samsung scaling chip that's found in the 64D8000.