I've tried the Pro Speaker Breakout Cable before, and the sound sounds about as good as the speakers that are plugged into them. In some cases they end up a touch underpowered, but I doubt anyone is about to run out and buy some kick ass speakers to use with it.
It's better to buy speakers that are shielded and have their own
power supply, The Logitechs look nice. I'll be buying a set of the Logitech X-220's some time next month, There not expensive...But they'll suit my needs.
(I love the wall mount abilities of them)
depends on the speakers.. their whole sales pitch is "now you can use hi-fi speakers!" when in fact if you try to plug in a true homespeaker that'll most likely need at least 100W, it's gonna sound terrible.
Watts don't say a thing in sound quality, but only in loudness (and even then, it's more the decibal level than the wattage). 10-watts/channel is pretty average these days for computer speakers, and isn't at all bad.
And I agree with Dolawren - make sure the speakers you get are shielded, if you have them by your monitor. If not, you can either damage the speakers, or send fuzzy lines up and down your monitor from interferance.
What Mac are we talking about - I think in the area of sound output you want to get specific on the Mac your using. For example a G5, why would you use the analog sound output to a stereo with optical sound input - use the G5's optical sound output.
I actually own the Pro Speaker Breakout Cable, I bought it for my G4 867 back in 2002 and had it plugged into a pair of Sony speakers that originally came with a large bookshelf stereo system. The CD player in that system broke, so I put it in storage and bought the Pro Speaker Breakout Cable to attach to those speakers.
I really can't say enough about it, I am by no means an audiophile but these speakers blow me away. They are much louder than my old Altec Lansing speakers with much less distortion at higher sound levels. The subwoofer on the floor always bugged me, I don't notice any appreciable loss of bass. In fact my fiancéé is constantly asking me to turn the music down.
I literally can't have my system volume set at a higher level than 1/4 of the way up or my speakers will make my ears bleed when I get the chime at restart. I edit with Final Cut Express and have always found the sound to be crisp and clear.
I currently use this cable and speakers with a 1 GHz iMac. This setup defiantely fills a room and I have used it with my iTunes during a few parties and it was more than adequate. I had a PC guy ask me where the amp was, I told him "in the iMac". He was impressed.
Again, I am not an audiophile and most of them would scoff at the thought of using this cable, but for my money it was one of the best purchases I ever made for my computer.