advice on buying a excellent quality BR-disk to test quality

Hello,

I am sorry if this is not the right newsgroup for my question but I
cannot find a more suitable group on the newsserver of my provider,
so...

As I have received a combi-drive that can also play Blue Ray discs, I
would be grateful to get an advice for buying a BR-disc of excellent
quality in order to get an idea of what BR can do. I am Dutch and what
I read about PAL, NTSC and HD-Video was not very clear to me. So,
though I do not know if this has any impact on your advice I suppose I
should mention the fact that I live in a PAL-country.

Thanks in advance,

Massimo