I found the specs for the Z-680s! It's only 450 watts of total power! That's weak! I'd rather get the Klipsch 5.1 500 watt speaker system. But, Logitech does support Dolby Pro Logic II.
ADVANCED SOUND SYSTEM MODIFIES EXISTING AUDIO / VIDEO SYSTEM INTO A HOME THEATRE PI Date : AUGUST 2002
TOTAL POWER OUTPUT 450 watts RMS
SATELLITES POWER OUTPUT 265 watts RMS (53w + 53w + 53w + 53w + 53w)
SUBWOOFER POWER OUTPUT 185 watts RMS
SYS FREQ RESPONSE 35Hz - 20kHz MAX SPL : 114 dB
SIGNAL-TO-NOISE RATIO : >100 dB (A) INPUT IMPEDANCE : 10,000 ohms
* Surround Sound Effects - HW decoding for Dolby Digital & DTS soundtracks, Dolby Pro Logic II (Movie and Music modes)
6 Channel Direct, Stereo x2, Stereo
WARRANTY: 2 years
SOURCE INPUTS : (1) Digital optical for DVD or CD players,
PlayStation 2, Xbox, or PC sound cards
(1) Digital coaxial for DVD or CD players or PC sound cards
(1) 6 channel direct (3 stereo-mini connectors) for 2, 4, or 6 channel PC sound cards
(1) Analog stereo-mini for portable CD, MP3 or MiniDisc players
PKG CONT: * 1 x subwoofer, * 1 x center channel speaker,
* 4 x satellite speakers * Digital SoundTouch Control Center,
* Wireless Remote Control * User's guide
* All necessary cords & cables (including digital optical & digital coaxial cables)
Simultaneously connect 4 audio sources, including PC, video game console, DVD, CD & portable audio player
* 8" diameter "long-throw" subwoofer with wood enclosure
In my opinion, it's pretty weak. BUT please keep in mind that these specs are from Austrailia and MIGHT change for the USA. The extra connections video games, DVD, and the WIRELESS remote control is pretty tight though.