the_lhc:You need to check the settings on the blu-ray player and the AV amp to find out which of those is doing the upscaling, if neither of them are, the TVs doing it (and doing it very well I'll add).
+1 on that. Just to add, that out of the box, I believe the Panasonic BDP will be set to upscale , so unless you've changed it, the Panasonic will be doing it.
Oh yes, on your LX5090, it should say what sort of signal it is receiving from a source, it it says 1080p for a DVD in your BDP, then it's the amp or BluRay.