Speaker connections
Fire,
Those logitechs are powered PC type speakers. They must be connected to the included sub and can not be used seperately. The line level connections to the logitech sub would require pre-amp outputs from the receiver which your model does not have. Either stick with the PC as the source or save for a speaker upgrade.
For $100/pair BIC and Athena are good options. For a $200/pair, check out the X-LS speaker from av123.com.