Only complaint I have is that the Logitech preamp is really of low quality but, that's expected since it's a $200 system.
One day I connected these speakers to my Yamaha RX-V559 and they sounded so much better. That kind of incited me to think about getting a quality receiver just so I can hook up the satellites directly to it and use the Logi preamp to remotely control the sub. The entry level receivers like Harman Kardon AVR-146 & 246, Yamaha RX-V363 & RX-V463, Pioneer VSX-818 & 918 will provide a world of a difference.
These are the benefits you'll gain by getting a separate receiver...
1. The ability to properly balance the volume of each channel as opposed to just having the option to adjust the Center, Sub, Surround.
2. You gain a much lower THD% with any of the above receivers vs the amp used on the sub that drives the satellites.
3. With the receivers, you will also get a higher Signal to Noise ratio.
4.When you increase the volume really high on the Logitech preamp, the front channels raise in volume more so than the other channels. With the receivers, you will be able to retain volume balance with all the channels at any volume level.
Then again.. these are computer speakers which aren't intended for the absolute best of 'quality' solutions since they are again $200. So all in all I'm very happy with what I got and don't regret at all what I purchased. I suppose if you are wanting to spike up a little more quality then a separate receiver will do some good.