The Panny 36PD30 only has 2 speakers and a sub, so has to employ Dolby Virtual to give the surround effects. You can elect to turn this off if you don't like it.
The Tosh 36ZP38, however, comes with 2 speakers and a sub built-in, as with the PD30, but also comes with surround satellite speakers for true Dolby Digital. I sent back 2 ZP38s, so I never got as far as opening the speaker parcel up and finding out whether they supply four satellites or five (ie. a centre speaker)!!
As I remember it, the ZP38 has the speaker connections on the back so that you wire the supplied satellites directly into the back of the box. The TV also has digital inputs to accept the digital feed from a DVD player, and then the TV can decode the signal into the relevant separate channels.
I think that's right, anyway - I didn't really pay much attention to the sound capabilites, as my TV is used primarily as a screen, with my amp and speakers providing the sound. I think that's how Panny are marketing the PD30 - it's aimed more at those who already have a dedicated sound setup and are out for the best CRT display you can get for your money.
Hope that's right (!) and hope that answers your question!!