Help me decide on a 5.1 System

I was saving up for the Logitech z-5500 but unfortunately they are just to expensive for me and I have realised I can't afford them.

So my next choice is out of the following three:

Logitech G51
Logitech Z-5400
Creative GigaWorks G500

Since I have had my hopes on the Z-5500 all the other systems I see their small faults. so I was hoping you could help me decide which would be nice and have good sound quality.

I currently have my 'Sonic Gear Blue Thunder IIR' 2.1 system for years. (and wow are they nice, unfortunately I cant find other sonic gear products)

So please let me know what you think is a good choice out of those three.

You might get more responses in the "computer audio" section.

Honestly, spending more than 10 bucks on computer speakers is not smart. Sorry to sound harsh but that's the truth. They are just pieces of plastic. Logitech THX speakers are just a rip off.

I'm going to quote some one from this forum "What exactly is THX agains?"

And another quote from a friend of my who owns a hi-fi shop "If something is labeled THX is equivalent of saying 'i am a piece of sh*t'"