If you are looking for a bass heavy system and well defined bass there is no more than Logitech. I also have Altec lansing ACS45.1 (which is also Quite good on bass oriented tracks). Another Altec’s i have is Newly CS21 which is also high powered 2.1 system of good Quality Sound and a lots of bass but which type of bass is on my Logitech Z-640 is Excellent Offcourse not for room Thumping like Z-560 But This System can easily shake your walls.
The fact you should know that for dolby digital systems it is necessary to have more power on center Channel because it acts like a Dialogue-Box the two other 5.1 systems i have checked are Creative Inspire 5200 5.1 and Altec’s 251 5.1 but both have low bass response and same RMS power to the Center channel which is not good to deliver a true Dolby Performance One other problem in Creative Inspire 5200 5.1 system is that either this set is 4.1 or very low powered 5.1 because its center channel doesnot work or work at very low volume and the second one Altec’s 251 which has better crisp sound than logitech but this system distorts easily means doesnot have raw power and after distortion you must have to turn down the bass because sound becomes fuzzy The Logitech Z-640 does not distort on my checking on Audigy 2 Value sound board the system consists of a sealed Subwoofer enclosure means no air flowing ports, the ported subwoofer design throw large amount of bass but in a limited frequency spectrum or range but a sealed enclosure subwoofer design requires more power from the amp and give a wide frequency response trust me, Some people say that music is not good on this System but You must remember the price and afterall this is not a big problem if you have a Creative 5.1 SB live or Audigy Line of Sound card you can easily fix it in seconds by Adjusting terrible slider to about 80 percent and bass is on my thought 30 percent in Windows mixer( bass level on sub set to top)
Finally The logitech Z-640 is very good in Movies and gaming In this price Tag you can’t beat the Z-640.
Good design and placement of control on center channel
solid and heavy bass in its class
Average sounding satellites(After tweaking very good)
Long Wires of satellites 6 ft front & 12 ft rear
Satellites sounds not so good without a good sound card
The bright blue light is terrible(can be fix from a electric