PC multimedia speakers with optical ,digital co-ax

My room size is 7 m * by 2. 5m and the area which the 5.1 channel speakers is going to be placed is a area of 3.5 by 2.5 m

I am getting a P4pE with on board sound max card
1) Utilizing either analog, (best for audio), optical or digital coaxial (best for DVD movies)
2) Most people, I would reckon inputting them onto an AV receiver

QN 3) I wanted to see if I could connect it directly to 5.1 multimedia speakers


A) For 5.1 DVD Playback , I THOUGHT OUTPUTTING This WAY INTO OPTical or digital coaxial would yield much better sound than analog . can somebody enlighten me why is tom hardware review mentioning that Megaworks 550 5.1 has better quality than the Prologic z 680 that takes in the optical and digital co-axial but not Mega works ?

a) The only speakers I found with the above optical and digital co-axial inputs is Klipsch promedia GMX D 5.1 that costs US 700US. OR IS THE PROLOGIC z680 (400 US) as comparable in quality ? ( THAT's The cheapest I FOUND)

b) IF Prologic has the best quality, would we get even better quality by paying 50 US more for the traditional combination .

a Yamaha 430 /Marantz 4300 receiver with a respectable set of 5.1 speakers & subwoofer such as Yamaha’s NSP 230.



5) Moreover, If I am not mistaken, I would have to get a certain software like theatre tek 2 to decode DTS, and DD (AC3) whereas a receiver can do all that. Z 680 decodes DTS, DD , but not DD EX or DTS ES .