DVDs on a HDTV from a connected PC (DVI or VGA) vs. from a DVD player (HDMI connection)

I have a few questions regarding viewing DVDs on a HDTV from a
connected PC (DVI or VGA) vs. from a DVD player (HDMI connection).
Is there any difference in quality at all?
I am planning to buy a 1080P HDTV, and since I already have a nice 5.1
speaker set and awesome sound card in my PC, I was thinking on getting
a wireless keyboard/mouse, HDTV tuner card for the PC and have a full
5.1 system using the PC instead of having to buy a new sound system
and DVD player to go with the TV.

I don't usually watch regular TV (I don't even have cable!) except for
the weather forecast in the mornings.
I do, however, watch lots of movies, and like to have the best quality
possible.
I live in a small apt in NYC, so consolidating the TV and PC, will
give me precious extra space once I get rid of the PC desk.

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