Best Sound Quality--Why?  The Klipsch Promedia 5.1 Ultra or THX remains one of the best sound systems available for your computer. Klipsch designed a high-powered, efficient 470 watt power supply and matching amplifiers to immerse the owner in games and movies.  Klipsch built its name in speaker design: the satellites'  tweeter, woofer and crossover reproduce music with crisp detail. Other computer speaker makers cut corners by stretching a single driver to reproduce frequencies from 120 or 200 Hz up to 20,000 Hz.  Klipsch uses a more expensive tweeter and woofer design.  Their tweeters use an efficient horn design, getting more sound per watt from amplifier power.  An upgraded sound card is not essential, but recommended.  Klipsch no longer produces the THX nor Ultra, and no computer speaker system matches it today.  Compared to the Ultra, the THX sub enclosure is a little narrower and has the port in the front.  The THX draws less current at idle than the Ultra.  Rated maximum output is within 2dB of each other.

Two specifications worth comparing:  True (rms) power at the ears (efficiency) and distortion (THD).  It is easy for manufacturers to inflate power numbers to look impressive using momentary short-circuit 'peak' power claims.  What truly matters are the RMS power ratings, if a manufacturer will publish them.  THD (Total Harmonic Distortion) becomes audible around 10% and higher. Klipsch's satellites are listed at 1% or less and the sub at 3% or less.  (I'm not biased against Bose--I enjoyed a pair of their top 901s for many years, but it is troubling that their system power and distortion specifications seem to be unavailable).  Klipsch's strength is in speaker design: the satellites'  tweeter, woofer and crossover reproduce music with crisp detail.  They are also efficient, getting more sound per watt from amplifier power.  If a speaker design is just 3dB more efficient, the result is the same as if the amplifier power were doubled!

Accurate bass vs. thump: Klipsch's dual 8-inch subwoofer drivers have 22% more surface area than a single 10-inch sub. The sub was not designed to impress with peaky, boomy bass, rather to accurately reproduce lower octaves of music (in addition to rumbling games and movies) as low as 25 Hz.

System Requirements:  An upgraded sound card is not essential, but is recommended for clarity. Good speakers will expose the weaknesses of your sound card that you might not have noticed before.  For example, my desktop computer has a Creative Labs Audigy 2 ZS sound card.  Its software also compensates for MP3 compression.  When I compare an Ultra 5.1 on my laptop computer using its basic sound card, the decrease in performance is stark.

A weakness overcome: I noticed a recurring problem with power supply failures when I bought my first Ultra as-is in 2005.  Klipsch made some improvements with later panels, and I've installed a fan system to remove internal hot spots.  With some air circulating inside the sub, the aluminum back panel can now more efficiently remove the system's heat by convection and radiation.  Other than a direct lightning strike that took out APC and Belkin UPS units along with my original Ultra 5.1, I've had no problem with amplifier failure for our 5.1 system.  I know of about 150 to 200 others who have added cooling to ProMedia 5.1 systems to extend their life, too.

Raising Expectations: Klipsch Ultra or the earlier THX 5.1s can spoil you.  A Klipsch Ultra 5.1 was my introduction to Klipsch back in October 2005.  I started to hear bass information and detail in the midrange I had been missing at my computer.  That led to buying Klipsch speakers and subwoofers for the TV / living room.  Impressive as it is for computer speakers, the Promedia 5.1 is actually near the bottom of Klipsch's product line.  As you begin to enjoy some of the best speakers at your computer, you may find Klipsch raising your expectations for your home and mobile sound, too.

As could be expected of a system a few years old, a couple of features are not offered:  the remote volume control is wired, not wireless.  The sound input is analog, not digital.