i'm want to upgrade my pc speaker...as title above which one better to buy and value to me? 

Creative MegaWorks THX 5.1 550 - rm550

Specifications

Power Rating: 500 Watts RMS
500 Watts System Power

Satellite Speakers: (Rated @ 10% THD @ 1kHz) 70 Watts RMS per speaker (x 4 speakers)
Center Speaker: (Rated @ 10% THD @ 1kHz) 70 Watts RMS
Subwoofer: (Rated @ 10% THD @ 1kHz) 150 Watts RMS
Signal-to-Noise-Ratio 99 dB
Overall Frequency Response: 25 Hz to 20kHz
Cables
Front Left, Right & Center Satellites: 3m / 9ft (RCA Gold plug) (Open ended bare wire)
Rear Left & Right Satellite: 5m / 16ft (RCA Gold plug) (Open ended bare wire)
Triple Line-In Audio Cable: 2m / 6.5ft (Gold - plated)
Volume Control: 2m / 6.5ft (Color - Black)

Sockets (refer to the Back Panel of the Subwoofer)
Audio Inputs: 3.5mm stereo mini jack
Front: Lime Pantone 577C
Back: Black
Center / Subwoofer: Orange Pantone 157C
Auxilary: White
Speaker Outputs - F/L & R/L: White RCA Socket
- F/R & R/R: Red RCA Socket
- F CENTER: Black RCA Socket

Volume Control: DIN
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Creative GigaWorks G500 - rm550

Specifications

Speaker power: 310 watts total RMS power

* Front : 36 watts RMS per speaker
(Measured @ 8 ohms @ 10% THD @ 180Hz to 20kHz, two channels driven)
* Rear : 36 watts RMS per speaker
(Measured @ 8 ohms @ 10% THD @ 180Hz to 20kHz, two channels driven)
* Center : 36 watts RMS
(Measured @ 8 ohms @ 10% THD @ 180Hz to 20kHz, one channel driven)
* Subwoofer : 130 watts RMS
(Measured @ 6 ohms @ 10% THD @ 35Hz to 180Hz, one channel driven)
620 watts total Peak Power

Frequency Response: 35Hz to 20kHz
Signal-to-Noise Ratio (SNR): 85dB
somebody can tell me ur experience if u have used before...and make me decision which one better

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Added on April 19, 2008, 1:52 pmno somebody give me any idea Or opinion?

to user this 2 item..please help me..now i consider to get Logitech Z680