[quote name='sarausagi']If these truly support dolby digital, dts, etc, can someone tell me how you control them? Is it via the computer? Buttons on the speakers? Or something? I ask this because I switch between 2 channel, Dolby Digital, Dolby Prologic, DTS, and multi channel several times a day, not to mention switching sources [PC, DVD, SACD, PS2, TV, etc][/QUOTE]
You can hook up any analog source to this, including 5.1 analog sound cards which use 3 stereo (or 6 mono) cables. You can also hook up any digital source which uses coax or optical connections, such as the ps2, xbox and many high end sound cards. the ps2 uses an optical connection and i think all creative (at least live and audigy) use coax. a few sound cards have optical, which is immune to emi on the cable but easy to damage, but most have coax, which can be affected by emi but is much more resiliant to physical damage.
Keep in mind, there are a limited number of inputs, so if you have 4 components they wont all be able to be connected directly to the unit at the same time. So either the connectectors will need to be swapped continuasly or it needs to be accompanied with an audio selector switch or some kind of mixer (think dj equipment).
I dont know how this setup works, but my yamaha pc speakers with dd5.1 and dts overrides any other signal if an optical signal is present. so if i turn on my ps2 which is connected via optical i no longer get any sound from my pc, which is connected via digital coax. and analog isnt even allowed to play without manually flipping a switch in the back to analog. since i dont have any logitech systems, my guess is that you can run one analog source, one digital coax and one digital optical signal at a time as it probably wont play two sources at the same time. and it cant play two digital sources without 2 processors. Youre probably going to have to switch between sources with a button, but only from 3 connected sources.
The 5450 on the other hand has 7 inputs, including 2 optical.