John,
As for HD-DVD if there is a difference in picture quality between the XA2 and A2 from my limited comparison of the two I can't say I've noticed a difference, that may change with more viewing but I don't think it would be significant.
For SD the A2 does a very nice job regarding upconverting, but to me there is a very noticeable differnce between it and the XA2 with the Reon processor. The XA2 makes SD DVD's look better than any player I've ever owned, the picture quality is sharper and better defined to the point where some SD movies almost look like they are in HD. To me spending the extar dollars on the XA2 just for the Reon HQV video processor was worth every cent.

A computer once beat me at chess, but it was no match for me at kick boxing.