I took delivery of my Z5500's today. Having read other people's reviews, I was expecting them to large. However, they are huge. The control unit is over 20cm tall and is now dominating my desk.
Setup was reasonably straight forward, and I had them working with the analogue input very easily. However, getting the speakers to use the digital connection on my soundcard was quite tricky and counter-intuitive. I have a SoundBlaster 5.1 Digital card. This is how to connect them:
1) Buy a 3.5mm to Coax connector (£1.99) and a coax cable (2 metres should be plenty, depending on where you want the control unit in relation to your PC)
2) Connect the coax cable into the back of the control unit and the 'Digital Out' jack on the soundcard.
3) Go into the 'Creative Surround Mixer' and select "Digital Output Only", Disable "AC-3 Decode" (you want the speakers to do the decoding) and then select "2 speakers" (Weird, I know. But it works)
4) In your DVD software (e.g. Windows Media Player, Power DVD, etc) you need to select SPDIF
Now the soundcard should pass the signal straight through to the Logitech Z5500's for processing and you should get true 5.1 sound.
Anyway, back to the speakers....
I watched 'Master & Commander - Far Side of the World' to test them out. Wow! Dolby Digital is crystal clear, loud and totally distortion free. There are loads of different audio settings - music and TV sound great using 'Coax Stereo x 2' (this setting uses the sub, front and rear speakers to playback 2 channel audio).
If you're planning on using these speakers to play games, please be aware that you'll have to use the analogue connectors unless your soundcard is capable of Dolby Digital Live (no Creative soundcards can do DDL).
These speakers are amazing. I think they're easily worth the money and I can't imagine wanting to replace them.
Buy them, you won't regret it.