Summary: I bought this setup for $80. Not bad at all for this little system. Used it with my xbox for a while and loved it. It shines much better for movies and games than for music. It sounds nice, but you'll be able to pick out plenty of flaws if your an audiophile.
Pros: Very cheap.
Cons: A little grainy on the highs, can be very unbalanced tonally
Summary: Low prices on these, which if your looking for a cheap 5.1 then its not too bad.
Sound quality is what you would expect from a set under 100$ and the bass is surprisingly powerful for its size.
Summary: I have had these speakers for almost 6 years now. Downgraded from my old Logitech Z680. The sub of the Logitech Z-680 had a buzzing sound within a few months of use that forced me to set the bass volume to less than 10% (although it was sufficient enough for decent bass).
Pros: Great sound for its price, durable, easy to assemble.
Cons: Front speaker cables may be too short, sub is exposed and may be prone to accidental damage
Excerpt: Logitech's X-540 5.1 speaker system has a lot to recommend it. The speakers sound great and the fit and finish is outstanding. Logitech has done a great job of packing some excellent performance into a small package that will fit nicely on and around most people's computer station.
Excerpt: Logitech X-540 Multimedia Speaker System (5.1) Beautiful, crisp, clear sound. Amazing, stunning playback. I have had nothing but positive results from these speakers. They sound better than most higher costing brands that I have tried.
Excerpt: We have been doing a couple of hard disk based media station reviews, thus we realized all this PC multimedia needed a nice outlet for sound; and who better than the friendly Logitech guys to ask for some product for review.