While i am somewhat of a geek, I am not hardcore.
when choosing media player, its simply this:
If you have a need for quality and already/planning to own a high end AV system ( $15000HK will suffice) go for a Sigma chipped media player.
Otherwise,
go Realtek chipped player, they are fast and budget.
I recognize this is not very comprehensive advice, but if you follow from what i have began here, it will take you to the right course. I personally owned both. A sigma one for my 40" and realtek for my 22". I have tested both players on my 40" with StarTrek (good benchmark movie) and the difference in quality is obvious.
Cheers
J