That Logitech system obviates your receiver.
It has it's own built in amplifiers but it doesn't look like it has a built in 5.1 channel decoder built in; i.e. this system will not accept a digital input. The digital to analog conversion will have to be done in your sound card, which must have analog outputs for this system. These are usually three 1/8" mini plugs, each of which has two channels.
You hook it's "six color coded cables" (analog inputs) to the six analog outputs on your sound card. You don't use the receiver anymore.
If your sound card doesn't do this, then this does not appear to be the speaker system for you.
Of course, I could be wrong...
And, Hi Ho has a good point. Some of these new "puny" speakers sound much better than they have any right to. I use these two channel speakers and you would be amazed at how they sound for their size.
http://www.alteclansing.com/product_details.asp?pID=VS2221