Subjective speaker analysis isn't an exact science; it's more or less me telling you how I feel these speaker systems performed after experiencing them for myself. Since that's fundamentally the same as a conclusion, I'm going to wrap both of these items up in the same section.
First off, a quick comparison of the three systems:
|Logitech Z-5450||Creative G550W||Altec Lansing FX5051|
|Wireless Surround Speakers||Yes (partially)||Yes (partially)||No|
|Wireless Headphone Support||No||Yes||No|
|MP3 Player Input on control||Yes||Yes||Yes|
|Remote can control MP3 Player||No||Yes (some Zen models)||No|
|Watts (Peak)||630||620||178 (est.)|
|Digital Inputs||2 Optical, 1 Coax||No||No|
|stereo-to-5.1 upmix hardware||Pro Logic II||CMSS||No|
|Integrated 5.1 Sound Card||No||No||Yes|
First, the Logitech Z-5450: this system is absolutely wonderful. There is no detectable background noise when using a digital input. The clarity is very good, the subwoofer outputs very strong lows, and although they're not perfectly defined they are still very good and powerful. The middle and high end of the audio spectrum also sounds great - it can pump out incredibly loud sound without noticeable distortion at maximum volume.
Frankly, this is a 5.1 surround system that's more suited to a living room's home theater than a PC. I'm not exaggerating: it blows away most of the sub-$1000 home theater systems I've heard. For your PC, this is using a sledgehammer to kill a fly. But when is being too good a bad thing?
In addition to the great sound quality, this 5.1 system offers a plethora of connectivity options, Dolby DTS and Pro Logic II support, a remote and flawless wireless connectivity.
I can heartily recommend the Z-5450 not only for the PC, but for the living room. No jest there: the system is very comfortable interfacing with a DVD player audio output, and its DTS decoder is a great addition.
Creative Gigaworks G550W
Second, let's examine the Creative Gigaworks G550W, another fantastic sound system. The entire audio spectrum was very rich: lows, mids and highs are great. Like the Logitech offering, the G550W can blast a lot louder, clearer sound than a reasonable person would ever want. Also like the Logitech offering, the G550W can easily do an excellent job in the living room home theater. The G550W is clearly aimed at the same market the Z-5450 occupies; the difference in what you hear from the two is subtle, but they're both a pleasure to experience, and are exceptional when the price is considered.
On the other hand, the G550W is missing some of the Z-5450's important features: no digital inputs is a really painful omission compared to the Z-5450, and DTS support is also a feature the G550W lacks.
Where Creative's offering pulls ahead is with some really interesting features that, if they happen to matter to you, might be really compelling. For example, do you consider wireless headphones important? If so, the system will automatically interface with a set of Creative's wireless headphones - the wireless transmitter included with the G550W is compatible with them. Do you have a Creative Zen MP3 player? The G550W is compatible with many of those as well, allowing you to control the MP3 player with the G550W remote.
I have no trouble recommending the G550W if these features appeal to you, in addition to its strong audio capabilities. It especially shines if you want to make use of its unique features, but it's an excellent 5.1 system any way you slice it.