I also own the X540 which is the predecessor of this system so it was good to compare new with old.
I have recently done a garage conversion and the room is being used as a TV/Cinema room. I purchased these speakers to connect directly to my Panasonic BD80 using the analogue audio out connections on the player. With the correct leads this provides `true` 5.1 audio for the room.
I also connect the other aux stereo input to the audio out of my tv via phono connectors. These speaker use a propriety `3d sound` process which gives very good simulated surround sound on this input. This is comparable with the X540 `matrix` mode but cannot be switched off however. Not really a problem though as it is really very good.
I have connected to the TV the following: HD DVD player, Sky HD, , PS2, Wii, and as mentioned a Panasonic Blu-ray player. The reason I am providing all this detail is to let you know you can have a good sound system in your room for around the 80 quid mark when wired up in this manner. In this respect these speakers fit the bill perfectly.
Soundwise they are fine , with nice high end and plenty of bass (adjustable via knob on sub). Power wise they are also adequate for an average size room, definitely loud enough to annoy neighbours.
I also extended the cables for the rear speakers easily by cutting the cable and adding a longer length to both.
I would say they are a step up from the X540 due to the additional stereo input which gives far more flexibility. Soundwise there is not much to choose between them.
I would recommend these to someone on a tight budget and as they are made by Logitech they should last a good while.